im guessing it has something to do with the thingy if its straight up but i dont think that would do that much...
"The thingy" is the ladder? It has to be vertical... the only thing that keeps the bubbles in place is the groove of the ladder.
If you get it level, the bubbles will travel at the same rate front and back.
I've read of people who keep a little of their mix and just add sugar and more water. So there must be still yeast alive for that to work. Yeast is so cheap I just change the whole bottle, and (for me) its easier to mess with known mixes. Reusing part of the old mix might make it produce faster
I dump the old mix into the toilet, simply because a flush is easier than running hot water and cleaning residue from the sink.