I have encountered this too. For me it seems to occur when I fill my party so that there is no space for the returning party. For instance, if my party maximum is 100 and I send a companion off with 4 troops, and while they are away I recruit beyond 95 troops, then this bug is activated. So, until it's fixed, just make sure there is room in your party for your companion and his fellows to come back. There may be more to it than this but it may be a workaround.