It might be a known bug, but I can’t find it in the Readme. When returning back from a secret level, the coins you previously earned in the level are lost. It can prevent you from going to the bonus warp! This is the case, for example, when returning to Medivo1 from Garglair. Other things than coins may be lost, but you might already know, or prefer you testing it?

Thanks for the report. Do you recall what the behavior is in non-Plus JJ2?

Yep, as I tested it along the way. When you came back from the secret level, the secret level warp event wasn’t disabled, and as you respawned on it, you were sent again to it indefinitely so remained stuck in the secret level. In my memory, secret levels never really worked in vanilla JJ2 and were something JJ2+ made usable. So that coins bug was probably already here, but was hidden by another more important bug!

But I’m not sure to be right according to the references to secret levels in the readme:

• 07-03-2008: Removed constraint where secret levels sometimes cannot cycle to other levels.
• 04-08-2010: Re-added constraint where secret levels cannot cycle to other secret levels.
• 06-10-2010: Fixed Area Warp Secret event and Area End Of Level event with Secret set to 1 so that the event cannot later be retriggered when the player returns to the original level after playing the secret level(s).
• 04-06-2015: If you end a level with a bird companion, it will still be with you when you begin the next level, just like in JJ1. (This doesn't fully work with secret levels yet.)

I think I recall the update of June 2010, where JJ2+ came with a level to present the secret levels functionality. I don’t know what the previous ones did. I never saw a secret level cycling to other levels…

It seems the last notice shows it’s known that the character’s possessions are not well managed with secret levels. I also think you warned us about that bug of lost coins with the update of 2010, but it still deserves to be written somewhere in the readme then.