ASUS RT-AC57U Wi-Fi speed problem

I have a very low Wi-Fi speeds on my ASUS RT-AC57U. Less than 30 mbit/s at 5GHz is ridiculous:

This is not signal issue, no matter I connecting from distance or putting phone directly on the router. Link state is excellent.

And 2.4GHz performs even worse:

I've tried to change avaliable settings, channels, operating modes, etc. Only managed to make it worse.
So, anyone knows what else I can try to do?

P.S. Stock asus firmware doesn't have this issue and easily operates 200+ mbit/s at 5GHz. And also obviously this is not connection/ISP or router CPU overload issue. Connection via ethernet port works great:

The driver has seen a few version bumps in the past few months, so please share which one you're using.

# opkg list-installed|grep mt76
1 Like

Thanks for replying. Here it is:

kmod-mt76-core - 4.14.141+2019-08-22-2a0edbb4-1
kmod-mt7603 - 4.14.141+2019-08-22-2a0edbb4-1
kmod-mt76x02-common - 4.14.141+2019-08-22-2a0edbb4-1
kmod-mt76x2 - 4.14.141+2019-08-22-2a0edbb4-1
kmod-mt76x2-common - 4.14.141+2019-08-22-2a0edbb4-1

Pinging @nbd he might ask you to run some tests.

I have the same router, running a 19.07 build, just tried the DSLReports test on my phone; I got 60/28 Mbps (line itself is 100/35).

Hmm. I flashed 19.07 from link in your profile. Unfortunately, results still the same.
But new system looks nice.