character is occupied

So me and my friend have a world on co-op and we haven't played in a couple months or so but we wanted to log on today and play but they had a problem with there character saying that character belongs to a different person but they played on that character with the same account? So we need help

DEAR StardewVallery developer: Since version 1.6 updata,EVERY TIME I go into my friend's farm(my friend is the host) and want to select my character,it says 'Character is occupied' and the character is gray (can't be selected). When I searched for solutions online, I found that there were SO...