thank you for letting me know. it may be one of two issues:
if you die or reset the level, the gem bag is emptied. this is a result of the way the save system is recorded and is not possible to fix without completely rebuilding the way the game works. an unfortunate oversight on my part.
however, the mere inability to sell gems may be due to the changes i made to their functionality before the patch. i'll investigate this and hopefully get it fixed. thank you for bringing it up; i was completely unaware of this.