I believe I'm almost through the game, but I'm having some issues with what I assume is the end boss (so...you know, spoilers and such, don't read on if you don't want the end boss fight spoiled)

After beating him up top, going down and getting on the rocket the tactic seems to be flying to the end of the corridor, grabbing an orb, shooting his hands, then his body once he's in the lava. Repeat a few times and once you're almost down a corridor to get more shots, he'll raise the lava level.

My issue is he often seem to climb too high and clip right through the ceiling. Afterwards, even when the lava's gone down, he won't come back down again. Is this part of the boss, or a bug with the boss? And at any rate, has anyone got any sage advice on how to defeat Razorbeard when he does do this?

Nevermind, it turns out it was a question of plenty of patience.

The boss will, for me, often disappear above the playfield, but the lava won't rise again until after you're halfway down a hallway. So just keeping the shots handy and circling around a while after the lava has gone down, and the boss will drop to a position you can hit him from. Just takes a bit of patience.

I was having the same problem and thought it was a glitch with the PC version.