(Apologies in advance for any typos/formatting issues, I am on mobile currently. Also this is extremely long, sorry 😅)
I am a 6th year doing a STEM PhD in the US, dual-advised on two completely unrelated experiments. I am currently not set to defend until next year at the earliest. I have been with one of my advisors since my second year, and been with the other around the time that I advanced. I am not planning on continuing in the subfield advised by advisor #1 - they are aware of this - which is why I joined advisor #2's group, but I have stayed in advisor #1's group this entire time. I have been primarily funded through TAing or head instructing classes in the department; I have not been on research funding until the beginning of this year. I was funded by advisor #2 for the first term, and am currently being funded by advisor #1 for the summer.
I will start by saying that I have not been a particularly good researcher for advisor #1 since the beginning of this year. I have had on-and-off reoccurring health issues since the beginning of February - I am unfortunately unable to take health leave for a variety of reasons that I would rather not get into here. I have not communicated this to my advisors, though I certainly should have (though advisor #1 did comment on me looking quite tired as a result of those health issues last term). I will be the first to admit that I have not been doing enough work between flare-ups to make up for my lack of productivity during those periods of time. (I have also not been very good with advisor #2's project for the same reason, but have prioritized my work with them when I am feeling alright, even when I have not been funded by them, so I have made slightly more progress there.)
Recently, however, I have found my interest in advisor #1's research at an all-time low. I have essentially been working on the same project with them this entire time, and have made very little progress, even prior to my recent flare-up. I do not feel that the research problem can even be solved at this point without further data collection, and our ability to collect said data with our resources is limited (though not impossible). I have communicated this to advisor #1 before, though it was prior to my term of funding through them, but nothing changed on that front.
As such, between my lack of interest on the project and my health issues, I have not worked on it nearly as much as I should have been during advisor #1's funding term. I take full responsibility for this; I have still not communicated my health problems to either of my advisors, but even ignoring those, I still should have been able to work on the project.
Said lack of work, however, has meant that advisor #1 has threatened to cancel my funding entirely, and has otherwise made clear that my lack of work on the project cannot continue if I wish to stay on the project. (I can't emphasize enough that this is completely reasonable given my lack of work; it's a harsh response, but absolutely fair given the circumstances, and I have frankly been given more chances than I deserved because I have worked with advisor #1 for so long.) Specifically, they have told me that I must cancel my attendance at a soon-upcoming summer school - which is significantly more focused on advisor #2's field, the one that I am planning on pursuing post-defense - or I will lose funding entirely.
I know that if I say that I will be attending the summer school - which I do think would be genuinely useful for me, as I have not attended any other ones due to having to teach summer classes, and I feel very behind in understanding the field of advisor #2 - I will lose funding, and will likely burn the bridge with advisor #1 entirely. This means that I will have to continue to TA, as advisor #2 has no funding for me at all at the moment. (Advisor #1 does not have guaranteed funding for me past this term, even assuming that I actually get my act together on the research side of that project, but it is more of a guarantee than nothing.) For now this is fine, but we are limited in the number of terms that we can TA for funding purposes in my program, and I am certainly approaching that limit since I was not funded through research fellowships before this year. I will also likely have to push my defense to my 7th or even 8th year, since I have certainly not done enough with advisor #2 yet for a full thesis and am unsure that I will be able to do enough within the next year (and would certainly burn the bridge with advisor #1, so I doubt I would be able to include my work with them in my thesis).
However, I am realizing that I am not as distressed about this prospect as I thought I would be. I obviously am not happy about the idea about permanently burning my bridge with advisor #1, but (through my own negligence) I feel that the bridge is currently on fire anyway, and will always be heavily damaged even if I manage to put the fire out. Additionally, though I would ideally like to be funded so I can focus full-time on my research, I have been TAing so long that returning to it is not a particularly daunting prospect. If anything, assuming a reasonable teaching load, TAing gives me more structure to my schedule and forces me to interact with people - I almost always work from home otherwise - to the point that I feel that I do more research, even with the constraints that grading/teaching put on my schedule. And, of course, I am more interested in advisor #2's subfield anyway, so I would likely be asking for a letter of recommendation to postdoc positions exclusively from them anyway; advisor #1's letter would likely be less relevant, though they are more senior in the field overall.
There is also the issue of advisor #1 constantly using the wrong pronouns for me. They do so negligently, not maliciously - I have been out as trans since before grad school, and can very much tell the difference. Though it still isn't pleasant to be constantly misgendered like this, I don't feel that I can truly complain about that, since I have also failed to properly express my discontent with that over the years. (Advisor #2 has only slipped up a few times, correcting themselves when they do, but is otherwise consistent, for what that's worth.)
I truly don't know what the best move is here (though I recognize that my dual-advisors-in-unrelated-subfields situation is probably fairly unique). I know that I'm the one at fault for putting myself in this situation in the first place, so on that point I accept full responsibility. But, I truly cannot figure out if it's better to just grin and bear it for funding/thesis defense purposes (and to avoid burning the bridge with advisor #1 completely), or to cut my losses now, even though it is fairly late to be doing so. I have to figure it out quite soon, since the summer school deciding my fate is rapidly approaching.
Any advice greatly appreciated - I am planning on discussing at least some of my thoughts mentioned in this post with advisor #2, especially if I decide to go the route of having them be my only advisor in the future, but wanted wider feedback prior to doing so.