In the assignment activity, that is set up as a group submission activity and a student is a member of 2 groups that are in the grouping that selects the groups, the student is not able to select which of their potential groups they are making / editing the submission for.

The submission page displays "Default Group" but gives no indication that this could cause issues nor that their submission will not be associated with any of the actual groups specified.

Whilst the staff are given a notification of the state: This does not give them any specific information they could action to resolve the state, and no information is provided to the student that there is a potential problem ahead.

The likelihood that a student being in multiple groups is a "sensible" set up is debatable, so either the ability to submit should be prohibited or some sort of mechanism to allow the student to specify which group they are making a submission to should be enabled (much like the active group drop down that normally appears).