To add onto this issue, there is certainly something wrong with Studio handling undo in this case. When undoing after the union turns invisible from the above issue, internally the solidmodel assetID is wiped. If you publish again afterwards, this union is permanently invisible.
I made a model yesterday (16:41, GMT-5) in this game (two unioned hollow cylinders) and this temporary disappearing issue occurred. After publishing and seeing the unions go invisible, I just pressed undo to make them visible again (which works for some reason) and repeated my last action and saved and published the game again. In a real server joined via the website shortly afterwards, the unions were invisible but still physically there, and are still like this the next day. This sounds a lot like this issue, but this particular version of it seems related to this issue given how it reproduces closely alongside, and reproduces reliably.
If I export this asset after publishing and seeing it turn invisible, the solidmodel assetID for the Union is this:
If I export this asset after undoing and re-publishing, the solidmodel assetID for the Union is this:
I’ve added a log file to the DM for this scenario.
Repro for this:
Just now, 14:40 (GMT-5), I create a union, rename it, publish, undo because it turned invisible, re-rename it, publish again.
I go to this same place ingame off the website and it is immediately completely invisible.
If I close and reopen the game in Studio without restarting Studio, the union is still visible.
If I close Studio entirely and reopen it, the union is now invisible.
This is strange because the issue above did not happen to me initially when I reported the issue in this thread, and I’m pretty sure I was using the same publish > undo > repeat action > publish again workaround.