Here's what I got when I opened Poser just now and compared the Renders pane with the RenderCache folder

Closing the pane and reopening it doesn't make any difference.

Closing the pane, closing Poser, and restarting Poser (with the Renders pane closed, then reopening the pane) doesn't make any difference either.

Going to a different room and coming back doesn't make any difference either - I tried going to the kitchen, and then tried going to the material room.

Deleting an image via the renders pane and changing rooms or closing/reopening the pane doesn't bring up the missing renders.

Deleting an image (or two) via the Renders pane, closing the pane, closing Poser, restarting Poser, and opening the Renders pane again has the same effect as before - the undeleted renders from before show up plus a few, but not all, of the missing renders.

(N.B. I've been having Windows Explorer crashes the past day or two, so this morning before doing the test above I did the Windows sfc + dism thingy which said that all the corruption was fixed)

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).