The accumulation of ashes on the magnets has been a growing problem.  Living on an iron planet, everything that burns contains iron.  A snapping mechanism would be nice.  Maybe there could be another spring mechanism.  The easiest solution is to never destack the booster.  Empty the ashes & replace the incense sticks with the booster stacked.  It could be printed in 1 piece to make accessing the full stack easier or it could use more permanent, non magnetic farsteners.  A brush would be required to clean it when stacked but it already requires a brush to clean the magnets.  A test might be gluing the full stack.

Helas, it's not practical to change incense with the booster stacked.  It would need a tool.  Emptying the ashes would make a mess.  There are twisting tabs which could take less room than magnets. 

No more melting & no more sticks have burned to the bottom so far, but some have gotten close & they always burned to the bottom before the starship.