Both messages come from the manager-pays restrictions:

• You can only select meals included! — the manager pays, the member may select included meals, but Member is allowed to checkout in Weekly Subscriptions is off. The member tried to add a priced extra meal beyond what the plan includes. Either the manager enables that module switch, or the manager adds the extra meals themselves.
• Module not available! — the manager pays and the member tried to add items in an ordering module that is not ticked under Allow member to purchase outside included subscription (Manager pays).

Neither message appears when the manager is the one shopping for the member.