We found an error in the activity "Group Choice".

If a user signs up for one group then later signs up for a second group, he is removed from the first group if this group has already reached the maximum by another user's choice

1. In the group choice settings, "allow enrollment to multiple groups" is active, and two groups are chosen. The number of responses is limited to two for both groups.
2. user 1 signs up for first group
3. user 2 signs up for both groups
4. user 2 is involuntarily removed from the first group, when he signs up for the second group.