So, I fibbed a little when I said I owned three.
The third one came today, and it has a busted off relay. It would only stay off for five seconds. So I called GH, who called Sentinel for the RMA. Sentinel's QC engineer called me to gather data in order to troubleshoot. And true to form, he was an awkward dude to talk to. Super focused on figuring out what was wrong. I can totally relate.
I'm super bummed about this, because it delays my flowering startup. I'm considering getting a timer with 15 minute intervals and doing 15 on, 45 off until the low range recycle is fixed. I have flower jones.