How to sync 2x RLC-820A

[user_871892464443569_871892464443569]

Hello,
I am using 2 RLC-820A for a sport livestream via OBS. Both pictures are synced at the beginning and everything is fine but after some time the slowly start to get off sync. Both are connected with an ethernet cable (18m and 30m but I guess this should not be the problem) to a PoE switch.
Is there any chance go get the synced all the time? Like the have a clok or something like that and when the notice that they are not having the same time as the clock they refresh?
Best regards and thank you for your help
Robert