12.5 crashes, perma-pinwheel upon reopening session

[jonathan jetter]

hell of a day here- constant crashes from 12.5 with client attending a mix session.

reasonably sized session (~50 audio tracks, ~12 instrument tracks, a few FX returns, and half a dozen melodyne instances), but nothing i haven't done before.

CPU + Memory usage are nowhere near peaking.

crashes seem to be linked to autosave, as the last autosave is always exactly 5 minutes prior to the crash (my autosave interval is set to 5 minutes).

so i'm assuming that PT crashes because i'm doing a certain something during the new autosave.

this wouldn't be the end of the world, except when i re-open the session, it permanently pinwheels. i can re-open with plugins inactive, and then go through and activate them a few at a time (reactivating them all at once pinwheels again).

HD Native 12.5, OS X 10.10.5, Silver Mac Pro Tower.

any ideas? thanks in advance,