I hear you ... Having stuff we thought we'd finished with to keep coming up and knocking us down is way beyond frustrating.
I have found that if I can do a little sleuthing to try to figure out what got the old PTSD symptoms kicking back up that it helps me to restore my equilibrium a little quicker regarding the current situation.
Of course I've by no means come anywhere near mastering this yet, but every time I do accomplish it, it makes me feel very good.
Hoping you can figure out the current source of distress that's making the old sources of distress flare back up.