Here is a free bit of advice, based on the recent experience of some poor unfortunate.
If you enter into mortal combat with a lab boss in the final room, and you manage to elude and evade his fearsome attempts to disembowel you, but you can not land the killer blow within a reasonable time (read 5 minutes), then he will get bored and abandon you to your silly games.
If this happens then you are dead in the water and looking very silly.
The boss is gone which is the same as "you lose sucker", game over, see you later sport. The only thing you can do is to recall and start again.
This is not a bug but a little known feature of the game.