I have an assembly composed of several other assemblies, and, until now everything was fine but for 10 minutes I have had a small assembly that remains present in the tree but is no longer visible on the screen...
When I open this little assembly independently, ditto: nothing on the screen. On the other hand, if I open a part of this small assembly: it is visible.
In pj, a screen print where you can see the tree structure with the presence of the SPC-110A-CU500 sub-assembly but that you don't see in the image (this small assembly should be above the hole)...
Or have you not tried to delete your assembly (I don't know about me to replace it elsewhere or whatever) but since several SW versions delete the selected part and not the assembly, maybe a lead...
Anyway, this deletion must not have happened like that by a miracle.
Would the assembly or the parts in it not use the "SpeedPack" function because in this case the parts, faces... only appear if you have allowed them to be selected, and therefore displayed. If you hover your mouse around the graphics part, are there any entities that appear?
This typically looks like the unintentional removal of parts from that subassembly from the head assembly.
Since the recording of this subset was not done live but by a higher assembly, the preview did not update. This would explain why you see the parts for a fraction of a second when opening this subset, the time it takes for the view to refresh.
If you have access to the MyCADTools suite, you can run VersionHistory which will show you the last operations on the subset file in question.