Mikrotik Chromecast/Spotify connection dropping

Hey guys,
I have a weird problem with my chromecast audio on a Mikrotik hAp Lite ac.
Streaming music via spotify on the chromecast, the playback randomly interrupts in intervals between 10sec to 5minutes.

Other services, like streaming radio stations work just fine. Also, streaming spotify on a mobile phone/computer works fine as well, so i don’t believe bandwidth is the issue.
The hAp ac is running with out-of-the-box configuration.

So far i tried the following:
-connected the chromecast to an old Linksys router running dd-wrt which has only 802.11b/g: Spotify playback went without interruptions! So it has to be a problem with the mikrotik.
-tried out a hAp Lite (non-ac): No difference.
-disabled Firewall in the quick settings: No difference.
-set up a QOS Route with the MAC Address of the Chromecast: No difference.

So, i don’t know what to do next - does any of you have the same issue and/or an idea on how to fix it?

Regards
Ludwig

Do you solve your problem? Now I have problem where I can’t connect Chromecast Audio to my WiFi