Xbox Live issues

Hello,

For half a year now I have been running a RB2011UAS-2HnD-IN with rOS 6.18.
It replaced a DIR-655 router from Dlink.
One problem I just cant seem to get fixed is solid connectivity for my Xbox 360.

Setup:
I forwarded port 3074 (TCP and UDP) and 88 (UDP) to my Xbox.
IP of Xbox has no restrictions outbound.

I am able to login fine, download games etc.
The Xbox connection test passes without an error. (NAT is good, not strict or anything)
But once a while (mainly after playing a game, or after login) Live seems to be unavailable error: 80072741.
I never had this with my old router.

Should the Mikrotik work 100% with Xbox Live?
Is there a test which I can do to make sure its not the router, or I can see it is?

Thanks.

Do not forward anything, clear all your rule on routeros and on xbox,
simply enable and configure correctly external and internal interface on UPnP and the xbox auto-configure all what is needed.

Tried this.
Disabled the firewall rules, enabled uPNP, did a Xbox connection passed and went fine.
Everything looked fine but still get the same error once in a while.

On the Xbox side I tried everything suggested by MS.
I get the idea the router is blocking something, but how can I test this?