There are two rather big issues for our online league where we play in Sweden with the first issue being the biggest one:
1. When simulating the league forward, with GMs "on vacation", the J20 randomly pulls players down to their team that are in the lineup for the seniors if they are of the J20 age. This happens for both players that are signed with the J20 team and players who are signed with the senior team. The senior team should have first dibs on the players. This happens randombly during the sims no matter the GM or vacation settings.
2. Another problem is that when your players