GHL Maxi Doser 2.2 AWC - Water Draining Non-stop Incident

Hello,

I use the doser with 2 float sensors. An incident occurred yesterday where the pump was draining the water non-stop causing my skimmer to run dry and almost causing the return pump to run dry. I do not know why the float sensor on the bottom did not trigger as usual. Perhaps it got stuck in the floating position. I've been running this configuration for at least a month with no issues. How do I prevent this from occurring in the future. Does the max on-time sensor work per pump (draining and filling) or is it for the whole AWC to complete? It would be perfect if it were for each function.