Hi Nat, thanks for your quick answer.
In my case, the overlay title was shorter than the clip, but indeed the number of characters was more than 26. Maybe, this could be the cause of the problem. I just resolved the problem by making 2 or 3 separate fixed overlay titles instead of 1 scrolling title. If you're interested, I could send you a short example of the sequence that didn't work (screen not cleared).
Cheers, Jac