Setting following eggtimer:

After a few seconds, checking the running timers shows this:

Then a few seconds later (Eventghost's log is running, but no eggtimer event appears and no OSD happening) it looks like this:

WTF? It appears that the timer, when setting 1 minute, just gently runs past it's time to raise the alarm and starts counting for another 24 hours.
I will investigate this weekend to see if I can find out where the differences might be between the two PC's (maybe version differences in Evengthost or of the plugin).