Yeah that sucks, but everything is destined to fail for someone. Yeah, plus always have it suck & container below dosing point and tubes out of the sump/tank water, so no siphon can occur! That is why we need safteys in place. Like using your apex to note if ALK exceeds say 8.6 & to cut power to the doser or a cal reactor.
I also make sure I really only have enuf ALK & cal in the holding container to last like 5-7 days. It's really not that hard to add to the container every 5-7 days. Takes 2 mins tops, and can be easily done when feeding or something. Plus if the doser decides to stay on it won't dump a ton of extra.
If you have to keep that much because you travel, well then you should have a controller and use it as a second failsafe to control everything to prevent these mishaps wether it be a doser, skimmer, heater, ATO, caclium reactor, etc, as these are all destined to fail