I´ve just tried to replicate that bug and it seems like that it happens when the penicel hits something completely parralel to it:
Picturs: https://we.tl/t-sT9IOqbhfd
( I am using WeTransfer since pictures are not allowed in posts. The link only works 7 days.)
So far i have not managed to replicate this bug on another collider.
I hope it helps.