This is weird, and I cannot reproduce it. Twice, I thought I'd found a fix, but it just pops up again...

Okay, so I've been importing FBX files, wrangling their scaling, textures and, too often, lack of hierarchy. Hint: Parent whole flock to dummy character. Fun over, close Poser...

Next start, Poser does not start completely, halts with UI half-loaded, its icon stays framed in orange. The window is often mucked-up, part of 'main camera' view often appearing where the library should be. UI Button response may be bizarre or incomplete. CPU usage spikes. GPU goes to 98+%, stays there. When Poser does finish loading, UI Response slows to crawl. Then you notice the camera is very, very slowly tilting upwards, so grid-lines and figure gradually fall off the bottom of view....

I first met this with 11.1 after wrangling an FBX that may have had an animation option. I learned to select 'stop' on the frames, clear the default loop option.

That sorta worked, until it didn't. Then 'Restore All' sorta worked until it didn't.

For my third take, I've cut undo levels to 30, set launch behaviour for document and interface to factory scene. Closed Poser scene, then Exit. That's two steps rather than just 'Exit', to be sure, to be sure. Next start, I posed LaFemme in swimsuit and fluffy wig, set that as launch scene. Since then, seems okay...

Question arises: WTF is going on ?? Why does camera animate without my bidding, and how do I prevent it ??

My Win'10 CAD Tower has 32 GB RAM, so a hypothetical memory leak may go un-noticed for a while...

just a couple of suggestions. Make sure that "use external binary morph targets" is unchecked. Also, did the message log say anything when you had the hang up?

Thank you. Took a while to find 'morph targets' checkbox in settings, but done. Have searched and found log, so now I know where it lives. Next time there's a hang-up, will look there.

Was okay until I re-imported a big FBX file to check scaling, then UI stopped responding and GPU went to ~55%, required hard exit.

Imported same FBX previously saved parented to dummy character. Similar but not identical sequence ensued.

Log shows nothing beyond the standard commands.

FWIW, I've even 'killed' the main-camera animation sequence lest that was responsible. No joy, not a clue. Ideas welcome, even on a '4x2'... ==

My current nemesis is a $3 budget robot from CG Trader. The FBX model (version 3) is hi-poly, high parts count, but not fully rigged. FBX is ~13 MB, imports inverted at ~1% scaling, requires parenting and 180º flip. Library CR2 ~48 MB. Loading one requires ~1 GB. Two plus LaFemme ~ 1.7 GB.

If Poser 'plays nice', superfly render with non-optimal lights but 24 pixel samples and 'progressive' gave

Ha ! Deleted both robots from scene. Reloaded one, side-shifted, loaded second. Lock-up and view-drift ensued, RAM usage soaring to ~1.9 GB before dust settled. Which is ~200 MB more than prior. A third loaded eventually, without camera drift, but taking P to ~2.5 GB. Fourth needed less RAM, 4@ + LaFemme ~ 1.1 GB total. Which makes no sense to me...

There are different 'flavours' of FBX. Take a look through Poser's FBX export, there are lots of options. If you can get one robot loaded, try re-saving it (don't overwrite original) and experiment with the options? Also, Autodesk have a free utility called FBX Review, might be worth trying to open it in that.

You mention a high poly count. How many polys in the robots? That might be the issue right there.