Thank you for the feedback. Unfortunately I still can not reproduce the bug, it works for me, when I set the col max to 4 and put the “I” upwards on the ground. :-(
As far as I see all report the same problem, it seems to be an issue with the I, that is all I know. But your report at least seems to indicate that it is not only at the end of a level, but can rather happen any time. Maybe I can integrate a work around where I detect that no new tile is spawned and then spawn another one.
Or maybe I should deactivate the I :-)