I'm still struggling to understand what is being speculated..
It makes little sense for UA to block non-stops but to allow 1 stop bookings. There maybe some glitch inventory sharing occurring on LH or UA's side but it is a strange situation if within a 24 window of LH intra-european non-stops are being blocked from UA MP awards - but all else is fine.
Probably worth wait a week or two and testing again.