Hi,
Based on your description, you have total 7 fans connected to TT Sync controller, and you have 2 fans plugged to the side that has sync issue, please correct me if wrong,
Can you try to swap the fans on port 1 and port 2, cuz it looks like the fan on port 1 didnt send commands to port 2, i assume both ports are functioning normal.
If all fans you have are Riing plus or Riing Duo, it is fine to plug total 9 fans to one TT Sync controller.