Photoshop truncating file names after a '.' when saving with actions

I have a series of 3d renders with sequential names like...

render.0001.exr
render.0002.exr
render.0003.exr  etc..

Previous to the new 2020 update, I could open these files in photoshop and run an action that would tweak various things then save a tif version to a folder on my desktop.  But now when I run the same action (or try to make a new action), the files save as 'render.tif' instead of 'render.0001.tif', so running the action on ten files in a row just repeatedly saves 'render.tif' over itself again and again.

That's a bizarre behavior change and affects my workflow several times a day.  I assume it must be bug because It makes no sense for Photoshop to ever silently change a file name like that.