Error when save in photoshop

1: Open Lightroom

2: Find a Tiff file with layers already edited in PS but now stored in LR and do Edit in PS

3: When PS is open, go back to LR and open 2 new files for edit in PS

4: In PS, drag those two newly opened files into the already opened file

5: Now the first opened file will consist og hte original tif file and two new layer with the other files.

5: File size is about 1.8 gb.

6: Do some editing in the file, like brush tool on layer masks etc.

7: When in PS, do save or save as.

8: Expected result: File should be saved back in LR with latest changes when doing save, and file should be saved to another disc when doing save as

9: Actual result: Error "Can not archive "_7503332-edit.tif" because an program error occured"

10: Try to convert the file to smart object.  Result: Same as over, not possible to save the file as smart object.

11: Other important data?  PS and LR version is last from 8. dec.2020. PC has 16GB ram, scratch disk has 616 GB free space. Old LRC and PS versions are unistalled.