You mentioned Cor 20. What outlet are you using? I would recommend plugging the Cor 20 into a wall outlet and outside the Apex energybars. This way if something happens with the bar the Cor still runs. I run 2 x Cor 15's and 1 x Cor 20.
Each Cor 15 is on its own eb832 (one eb832 is primary, secondary isn't used outside the Cor 15 so a standby). So skimmer and return pump. The Cor 20 is also a return line, longest plumbing, and plugged into its own wall outlet and circuit. This way I have redundancy with eb832's should something happen and return pump outside the Apex again for redundancy.
Best part is they all use the same plumbing so swapping out between any if one goes south is a 2 minute or less job. Great pumps outside that o-ring as you found out