Do you mean the post-Jam? There isn't really a pre-Jam version, just the one made for the game Jam (which is pretty buggy) and the bugfixed version I made after the judging period (which may also have a few issues, but not as many). But the Jam version is pretty broken.
In general the enemy collisions can be really weird. They're supposed to deal damage when you touch them, but sometimes the game gets a bit confused while they're moving and they'll just kind of slide right by. All in all I feel like their hit detection is generally reliable, and trying to make it perfect would be an immense headache, so I likely won't be trying to fix it.
And I wanted the end segment, particularly the Maze, to be fairly challenging. I had a few reports saying it was too easy, so I made fewer healing opportunities. If it's still giving you trouble the best advice I can give is to take it slow and really keep an eye on the Nymphs' movement patterns.
As for the Chase itself, it can be a lot more difficult when BB is at a higher weight stage. She herself is, as you mentioned, slowed to a crawl, so she'll have the runway flooded with Nymphs. The trick is more or less the same as the maze, as in you'll want to try and take it slow.
I'm working on a few more QoL adjustments for the Post-Jam and Browser versions, which will include saves just before the Maze and Chase sequences. Hopefully that'll help.