@M0YNG I think it's one of those things where accuracy takes a back seat to practicality. I have a similar issue here - I use VA7YK in Canada, but because I'm not a Canadian citizen, whenever I go to the states I switch to my UK call M0VKG as I'm covered under CEPT.
APRS is a fickle beast at the best of times as well - depending on the radio (or APRS client) messages sent to M0YNG-<x> might not be picked up by M0YNG-<y> - it's all down to the receiver.
Amateur radio - always complicated 😄