Following reports that several people had more than 7 players wearing personalised shirts.
I looked into how the rule might have been circumvented.

Here’s what I found:
You must have 6 players or fewer with jerseys.
You add a new player and start a printing job.
A line is created with 0 in stock for the jersey.
You cancel the player’s customisation and repeat the same process for the others.
Creating these lines allows you to get round the limit per player.
Once all the lines have been created, you can restock all the items.

Aymeric, could you please fix this bug/loophole?