Resetting Saved Variables

[Kraeius]

I checked each subject in Authoring Discussion category but couldn't find what I'm searching for. Can anyone tell me what are the conditions that make saved variables reset? Currently with each new upload, players lose their saved variables which is very annoying for them.

Probably I do the same thing each time, what can this be? Changing version in .txt or .lua? Adding a new variable? Changing name of a variable? something other?