Sorry you guys are dealing with this distraction! I've tried every lighting condition and simulator setting that I can think of, and can't reproduce it for myself. Clearly, I don't doubt what you're seeing, I just don't know how I can deal with it. I think it's likely the master caution/warning, but there is nothing I can do to control the screen-space reflections. Unlike shadows, if you can see the annunciators, then so can the shader. If you really think this changed with the last update to the TBM, then it would likely be caused by the cubemap I [reluctantly] added for the instrument glass reflections. I can give you two ways to test this, but one is a lot easier than the other:
If you go into the aircraft's community folder and locate cockpit.cfg, you can try changing the first line to cockpit_type = 0. If that solves the problem, then we know the culprit, but you guys may have to fight my users who want instrument glass reflections for the solution!