When something looks wrong
A trade was copied twice
Almost always a second copier running on the same account.
Replica copies each fill once. A doubled trade on a follower almost always means another copier is also copying into that account, for example TopstepX's own copier, or another copy app.
Replica flags any fill on a follower that it did not send as "Follower fill NOT sent by Replica" in the activity log. Turn the other copier off on that account: one copier per account.