Went to playlist and pressed ALT+T (Add new time marker)
Further tests:
If I added one manually from the menu first, no errors happened and it worked as intended.
FL Version 12.0.2. 64bit Producer edition
Windows 7 SP1 64bit ...
FLStudio for years without the problem referenced in the title. With FLS 20, however, I have this problem:
Let's say I make a pattern with a verse and a second with the chorus. I duplicate the patterns (i.e., verse ...