Hi! This is completely new.
Are you using the latest v0.2.1.1 version? and does the "stop registering all mana potions in possession" in terms of selling potions in the Request List? or perhaps the Town?
Thanks for letting me know!
I am on v0.2.1.1, I didn't try with the townsfolk, If I can reproduce the issue I'll try offering them around town and report back.
Edit: I'm attempting to repeat everything I did on my first play that resulted in the bug, but so far no luck. During that first play I messed with the rune book (nothing happened) before taking the letter and tour, then activated the request list a second time without a potion in my inventory and denied the request. Brewed a mana potion and consumed it. Brewed a second mana potion and placed it on the counter, then picked it back up and consumed it. Touched the crystal and named the tower. Went outside and planted an herb seed. Interacted with the town portal but did not leave. Dispelled the barrier to leave the tower area. Interacted with the second barrier leading to the WIP area. Entered the cave, and interacted with the spell circle at least 4 times. Went underground and interacted with all of the boulders. Interacted with the blue slime barrier and received the mana potion, drank it, then dispelled the barrier. Caught 1 blue slime and returned to the tower. Brewed 1 mana potion and interacted with the request list, and the list behaved as if I had no available potions.
Either I'm missing a step or just got (un)lucky on that first play.