I've only seen any in Level 5
It's impossible to finish stage 2 there sometimes, but not always.
When there's nothing left to destroy - even the 'S' key says there's 0 blocks left - the stage simply doesn't end.Sometimes you can actually see some blocks - S key stills says 0 left - but the ball/canon just flies over them.This could be due to a faller block or the explosions as there's a lot of dynamite in this stage, I don't know.
Elsewhere in Level 5, some indestructible blocks (the ones you can only move) can trap the ball/block areas for ever.
In both cases all you can do is start again, which is ok with me, btw, it's not the point.It's just bad luck.
Except that, some minor stuff nothing important.