Why does this happen?

That bug was fixed in S3&K. It has something to do with Super Sonic IIRC.

 

This usually happens when you rush ahead of the boss at start, and can see the capsule before the screen can be locked. When you go back and beat the boss, the capsule isn't there when the screen unlocks. I'm not exactly sure WHY this happens, but it's weird nonetheless.

 

Try loading the level into SonED and seeing whether the capsule has the Remember Sprite State on.

While I was making my GHZ boss act in Sonic 1, I noticed that if I ran to the capsule and back again it would disappear, because of the RSS bug in SonED2. It's probably the same thing happening.

 

In S2 and S3&K, it's the highest bit of the Y-position.

 

Lol, I wonder how many people this happened to otherwise, like on the console. That's what happens when you literally split a game in half.

 

Funny, this has never happened to me. Is it because you zip as fast as you can into the capsule screen? Because I just wait for the screen to scroll again.

 

never seen that, odd find.

 

No, you have to go into the capsule area before the boss, and then go back, for the bug to occur.

 

This has happened to me, too! Only once, though.
Very annoying. Wonder why it happens..

 

If you get sucked up as Super Sonic, you stay as him when you hit the capsule. =P I liked that one, cause the "Sonic" text looks much better when flashing yellow.

 

Y'know, I actually had this happen to me on my old Sega Genesis, but I never had it happen to me in an Emulator. I always just thought it was due to the fact that my Genesis is as old as dirt. lol. Either that or the fact that my Sonic 3 cart is a slightly beaten up one that I got at a pawn shop YEARS ago.

 

I remember that bug

 

thanks for this descriptive and truly helpful response, a three finger salute to you, good sir!

 

No problem.

I also have a fully detailed account of my response where I was when I heard of 9/11 in the form of "wow" and my indepth review of the Star Wars series of movies "shit", if you want to hear them...

 

I've once had a really weird encounter in that level. I came through that tunnel as Super Sonic and was running through the area where the boss is, but then not only did I pass the boss, the game messed up and the floor disappeared for like a couple feet and I could keep going until some far wall.

I think this was on my cartrige though, which was VERY buggy (the damn cart wouldn't even save my game data D, or it might have been on my Sonic JAM disc (which was very scratched up).