I've been making lots of stills from my timeline today and noticed that the files were being saved as bmp images.
Thought, ah yes, I've updated to 4.5, I haven't changed the setting back to psd.
I go into plugin settings, but still image is set for saving as psd.
Go back, save a still, still a bmp.

I changed it to tiff and it saved as tiff, I changed it to psd and it now saves as psd.

Thought I'd mention it.

Graham