There are quite a few reports of this over in Bug Report. Guild members appearing as if they’re from different servers, roster listings with incorrect info, and folks that recently transferred or name changed appearing with their old name-server info.
You might want to add your voice to those threads there as well!
A couple threads, but there are more:
https://us.forums.blizzard.com/en/wow/t/transferred-servers-guild-roster-bugged/1540832