Not sure if you can call it a bug, but certainly something weird and unexpected. I have a few FP objects thats was made with the "Generate" mode in version6.
Then on another pc, with version7, I switched the mode to per "Item", and deleted a few of the trees in the FP obect.
Back on the 1st pc with version6, opening the file again that is now in "Item" mode, results in no items at all. Trying to render, result in the FP error after the render saying to check the stats in the general tab, but the stats are empty, without warning or errors.
Also, these (corrupt) fp objects cant be deleted from the max scene. Selected them and pressing delete on the keyboard or from the max menu, doesnt do anything.
Both machines have Max 2021 update 2 and VRay Next update 3. ONly difference on machine has FP 6.3.0 and the other FP 7.0beta (the 1st beta for V7, not the 1st update or the 2nd update)