I can comfirm the exact issue. This also apply to making food instead of a potion and all potion options that I could test. I also tested both cauldrons. The potions can still be made from start to finish with no interruptions but if the player or the sim's surroundings tell them to stop, it cannot be restarted as the Sim simply walks up and immediately resets. The cauldron becomes unusable until you discard its contents, losing the ingredients and in one case glitching one ingredient, causing a different bug that prevents making the potion associated with the ingredient as the game is confused on whether or not the Sim has the ingredient required (but is fixable once another of the same ingredient is added into the sim's inventory)
This especially becomes a problem if a Sim has the curse of uncontrollable laughter and attempting to make a potion of curse cleansing to get rid of it, only for the Sim to get interrupted making the potion to uncontrollably laugh and, as a result, can't resume the potion, such is my case.