Your guess it might be interlooping with your therapy work sounds right to me; have you had a chance to ask your T what might be happening?

Sometimes hard subjects take a rest for a bit; one's physical/mental body can only take so much (my T explained it to me when I was wishing to cry myself to death and she explained how that's physically not possible, you just stop crying eventually for a bit). So maybe you did all your work and that was "right" for that time and you worked on something else and sort of rested and now are going for phase II, harder or deeper but now you're stronger.

Good luck. Sounds hard. {{{Typo}}}