interference ?? channel ??

I am using XBee3 one in a wireless remote as coordinator and 15 as end
they move move a linear actuators to to different points
they are used in fitness studios all around the world I have 5 location that work perfectly, and one that has random failure of not moving( respond the to the command it could be 1 or 5 that don’t respond how can i Fix this?
Is it interference?(noise) other devices and things in the surrounding area ?
what is the fix?
change the channel?
I have purchased 2 XCTU dongles can this be used to pin point problem if so how ?

Will switching from AT transparent mode to API mode reduce the chances of failure? ,

Or is it ok to use At mode for this type of application?

Can I continue to use At mode and will changing channel /frequency fix my issue?

What are the all the different thing that may be causing this problem?

I don’t think there is enough information listed here to know what the issue is. For example, which firmware version are you working with? With 15 end nodes, I would hope you are using 802.15.4.

If that is the case, you could try using a different channel. But run the Energy detect first to see which channel is best to use.

Hey mvut looking for some tech help
I have a XBEE 3 set to one specific channel
and detect I might be having interference is it better to switch to scan channel setting ?