Thanks for the file, Qray.
It opens fine here.
I can’t reproduce it with any options that I can think of.
If you like, use the upload link for the second file you mentioned. I will check it as well.
If I use the any “search” option, the material stays
If I use the “solo” options of the Layer, everything is gone.
No Takes where used, so I exclude that.
No sign of a script that could cause it.
Have you tried to open a second Object Manager? Just a thought.
Perhaps delete the Preferences, go to the Edit> Prefercens… (cmd-e) and use the Open Preferences Folder… Then search for the “CINEMA 4D.prf” file and trash it, perhaps save it somewhere as a zip file, if you like to reuse it.
One option would be to check if you can select all (cmd-a) and copy it (cmd-c), then open a new scene file and paste it (cmd-v).
If all of that isn’t working, and as you said it is not reproducible, please get in contact with the support:
https://www.maxon.net/en-us/support/how-can-we-help/
All the best
OM:
https://www.amazon.com/clouddrive/share/ukZhngkbXrHfGMStoJdXAvSLRaqCLAyTxhCWIlrJkQN?ref_=cd_ph_share_link_copy