I found this via Google: https://www.geekzone.co.nz/forums.asp?forumid=48&topicid=250858
I have a simlar issue. 30mA RCCD, got a flash new Cyberpower UPS... no issue for a while, as we didn't have powercuts, but now if the power goes out (me on the main board or an actual one), it flips the RCCD, even if there is no load behind it.
Other than taking it back to PBT and either getting a replacement, or a different brand... any ideas? I dont think I can get the RCCD removed, nor I think would I want to (this is in an external studio, and there is another one in the house on the mainboard....)