I decided to revisit my OpenGarage today, which has had this problem for a very long time. I started using a MyQ instead, but would prefer the OpenGarage to work.
Long story short, I got on the ladder and removed the top piece of the acrylic case. For the last hour it has only varied +/- 1cm, instead of +/- 3000cm.
I’m hopeful that I can just use this, since the MyQ has it’s own problems!