Amiga 40th release (July) is probably what you mention on the other comment as most stable and the one you use instead. It's done in Scorpion Engine from May, 2025.
When I switched to one from November, because requests of support to USB adapter on real Amiga, which Earok promptly added, it required moving to newest version of Scorpion, which in turn generated this whole list of issues. If you can list all of then, I'll be infinitely grateful. Yes, I got that candle hit + player vanishes on emulator. But not on real Amiga 1200 apparently. So, are you using emulator? If so, which one? It's quite an interesting bug. Also seems you only vanish if jumping or moving. If you're standing in place, you can hit it normally.
About stairs, I don't get such complains and I watched people playing seamlessly without issues during my Amiga expo 2 weeks ago at a local retro event, at least the 1st half of the game. But I know that in worlds 3, 5 and 6 we got some odd stairs that may flip or invert Simon sprite and play tricks. Also, if by f...p... you mean that Simon does a quick acceleration when starts upstairs? Again, that's a thing that seems to happen and is exacerbated on emulator, but quite subtle on real hardware. Bear in mind that stair errors happened in console versions done by whole teams (the famous moonwalk for example) and it's overall a nightmare, so much that Konami themselves kind of scrapped the idea and in Symphony of the Night they're handled more like ramps.
Lastly, I'm afraid to say that at his point I'm quite burned by this project, it was a hobby project but this kind of thing (stairs) makes it feels like an endless chore rather than pleasure hobby and it would probably not improve too much on that, other than fixing the mentioned broken stairs at levels 3 and up. It's my limit. As I have my own original projects on queue which I going to start soon (and rest assured, I will never use diagonal stairs model in any project, ever, it isn't worth the hassle).