Hello,
If I understand correctly, you are using RUTX50 as an access point to connect your devices and a client to some other station at the same time?
If this is the case, there is a known issue, which is being worked on at the moment, but does not have a resolution yet.
The only available option at the moment is to stick to 2.4GHz frequency band.
Apologies for the inconveniences.
Best regards,