Reported by Zamolxis : http://vcmi.antypika.aplus.pl/forum/viewtopic.php?p=2433#2433
Tavern may give hero with only 1 Lvl1 creature at the start of a new week, as if we already hired a hero that week. I had it happening only twice:
1st in 0.71(see forum link above): On Day 1 of Week 2 of Month 2, one of the 2 heroes which were offered at the Fortress Tavern in the beginning of the week was Jenova, Level 1 Ranger, with only 1 Centaur in the army. This should not happen unless we already purchased a hero or if she would be a retreating hero, which was not the case.
2nd in 0.71b: After purchasing both Tavern (Fortress) heroes in week 1, the 2nd (non-Fortress) hero in my Tavern at the beginning of week 2 had only 1 Lvl1 creature in the army.
I didn't manage to reproduce it. First I though the pattern would be that if we have 2 same alignment heroes at Tavern and we hire them both, then the bug occurs next week. But I managed to reproduce the scenario and had no issues at the beginning of the next week. So it must be something else. I'll let you know if it occurs again (and if it does, I promise this time I won't forget to save the Client log before starting another game:P)