I can assume that you have a separate rules for each node. Worth to check the rule for this particular node and compare with working ones.
This is an application, there is no magic. If something working not as expected, check what’s different.
Your port maybe openeded for the port checker, but closed for this particular satellite (you may be blocking somewhere in your setup only some IPs based on the range or the rule for this node has an error or typo).
Perhaps this satellite cannot reach your node only periodically.
You can check date time intervals, when your node were offline: