0 com.apple.time 0x000000010f87a25c power_set_handler + 57
I think this is related to the fact that sometimes random windows will behave like something is leaning on the RET key. But this is not "dirty keyboard" behavior, because it is attached to a window. If I focus elsewhere, the new window doesn't get the repeating key, but if I go back to the first window, it resumes! Also it keeps happening when every USB device is disconnected from the iMac.
AntiRSI is also acting as if there is constant user input and never going idle, even after I've quit all apps: the timer never clears.
This seemed like the sort of way that Rowmote Helper might malfunction, but no, I killed that daemon and it's still going on.
Also keeps happening after I nuke /usr/libexec/UserEventAgent.