Hi there,

Cause:

CTRL+C / CTRL+V are windows Commands and sometimes a problem happens between the SendMessageToWindow Event in Windows and between the AutoCAD recieving the Command

Solution

1)Close and reopn the file

2)Try running “Audit” (“Y” to fix errors) then “Purge” command to clear everything

3)Try”WBLOCK” Command

If this doesn’t work ,

According to AutoCad this is caused due to non-essential data from DWG files that have become bloated while copying and pasting from DWGs containing DGN linetypes.

you can find the fix here:
https://knowledge.autodesk.com/support/autocad/downloads/caas/downloads/content/autocad-C2-AE-dgn-hotfix.html

Which will prevent future occurrences of the file bloat issue from occurring.

Hope this helps.