Ahhh, THESE caves! I kept thinking about caves inside hills!
All right then... I'll see what can be done. Not even sure if it's bad.
Worms offer some challenge, because they can at least spit, but shamblers and big spiders are sitting ducks.
Another round of screenshots then, and I stop until you make up your mind if you want to make caves harder or not. Maybe there should be a separate tileset "Big monster caves", where most corridors are wide enough for them. I can clean those up, if there are some kind of ASCII source files for map tiles.
Worm 1 is stuck in a short corridor.
Worm 2 is stuck on the middle level, because the stairs down are too narrow (same as with spider queen above), and it cannot go beyond the stairs up. Is there too little place?
Worm 3 is stuck in a fairly large hall. Note that entrances to the starting/evacuation area are too narrow, making it completely safe.