Could I recommended trying band steering, this feature encourages clients to connect to the 5GHz band rather than the 2.4GHz band.
Further reading: https://community.cambiumnetworks.com/t5/cnPilot-E-Series-Enterprise-APs/Configuring-Band-Steering-on-cnPilot-E-series-Device/td-p/52985
You can find this under the advanced settings of your WLAN in cnMaestro.