Lamobo R1 very slow internet speed

Hello All!
I bought Lamobo R1 (Banana Pi R1) router, and incredible slow open any website (10-15 sec load), but previous router TP-LINK its all ok (fast). What is the solution/trick/tip this model, I've tried everything (I think)?! My internet type: 150Mb/s, cable (Telekom), and added for the modem in DMZ!
Thank you!

I did notice the same behaviour. I did few tests across available openwrt images, this is showing up on all of them.

Partially to resolve the issue I installed the 19.07.4 image where I did installation of mwan3 and repurposed two lan ports as wan ports. These are now running at full speed. I also repurposed the old wan port as a lan port, again, running at the full speed. I am going to test it further. For now it seems that switch reconfiguration during boot time helps a lot. Not sure, whether this is hardware or software culprit.