Cubase Keeps Changing Project Length

I have searched this forum and found several [old] posts regarding this - but no definitive fix.

I am setting the project length in the Project Setup Dialog - but Cubase keeps adding several minutes to it during an edit session, and I cannot for the life of me work out why.

Having read previous posts regarding the same issue, I have checked [and double-checked] that there are definitely NO events (notes, automation, tempo changes etc.) beyond the length I set - yet Cubase still insists on making the project longer [seemingly at random - at least I cannot work out any pattern to its decision-making].

Bearing in mind the checks I have already made, does anyone know why this keeps happening and whether there is a way to stop it?