Another lesson learned. Was watching TV the other night, I heard the overflow alarm from my Osmolator. Sprung up from the couch to make sure the ATO didn't get stuck on. Luckily, the water level was right at the float switch alarm max. After looking through the apex logs, it looks like the problem was the Apex rebooted randomly several times throughout the day. My Osmo is programmed to power off and defer power on after a "power outage". Each time the Osmo powers on, and because of my odd setup, the RO/DI PMUP powers up (I assume Osmo power on self test) for 17 seconds. 4 random reboots = 1 minute and 8 seconds of unneeded top-off water in my little BC29.
Now, I can get upset at the Apex for resetting/rebooting itself for no good reason or Tunze for ignoring their primary optical sensor for 17sec during power on or myself for not testing every possible failure scenario. Instead, I just added a "Defer 000:18 Then On" statement to my PMUP top-off pump outlet and posted here so that others can hopefully learn from my bone headed misadventures.