Hey!
I had a conversion with @gerrieg about that… It seems to be a timing issue at startup, and I sometimes have it for one device, at next startup for another or sometimes even for none of my devices. Cleanly setting up homegear or even OpenHAB2 did not work. In some testing with gerrieg we could confirm that if you setup OpenHAB2 on e.g. a PC (something that is faster than a RasperryPi in my case) that indeed the errors vanish.