I don't know whether this is something to expect when switching between snapshots and release version of Minecraft but I have noticed that anytime I use the release version of Minecraft in my creative world that all hoppers "forget" what they had in them and also leave things like comparators still powered falsely. This is affecting a project of mine using and item filter to play different custom songs and breaks the whole system meaning I need to rename all the items and manually reset the system.

Again, I don't know should it be expected but I'll post this here anyway. Attached is the inventory of one hopper in the system and showing the system still being "phantom" powered.