This happens intermittently in the current version in Debian testing. Usually it seems to happen in situations with hidden blocks, or use of the "explosive" ball, or the "exploding" blocks. Reproducible: Sometimes
This bug is repeatable in version 1.1.0 Repeat by playing game that has invisible/hidden blocks or blocks that started as permanent/unbreakable. In short, a level ends prematurely with blocks remaining. Perhaps the root cause is an incorrect count of blocks than can be broken.
Fixed with https://git.reviewboard.kde.org/r/128556/