Television service device(Sky Q) keeps disconnecting from the network with NextDNS enabled.

I have a problem with Sky Italy television service provider devices.
Recently I installed NextDNS on my router running OpenWRT at home. The morning after I woke up to discover that both Sky Q devices are disconnected and are refusing to reconnect to the wifi network again. I couldn't believe that NextDNS was to blame but as soon as I stopped it via ssh the connection on the device was up again. I managed to get MAC addresses for both devices  and to add them to a new config that has no blocklist enabled at all. The issue came back after several hours again. 
Since I have close to zero control over those two devices and the separate config didn't work what options do I have? 
And what I don't get at all why the issue occurs after a not so short period of time and not immediately?