Weird slow connection trought usb ethernet adapter

Hello, I’m facing a weird problem.
I have an 2011UiAS-2HnD configured as AP and I’ve worked with that two years without problem but, today I’ve bought and USB ethernet adapter(Ugreen USB 3.0 gigabit) to get wired connection to my Nintendo Switch.
I had connected the adapter to the console and the cable to the AP and all had connected at the moment.
But when I ran the speed test(on console) I’m only getting ~9Mbps(Download)/ ~15Mbps(Upload). And that’s an awfull speed(Trought wifi I get near 30mbps(down) 20mbps(up)).
I’ve tested connecting directly to the main router, and magicaly I get ~90Mbps(down).

I don’t know what can be missconfigured in the AP interfaces, I didn’t configured any limitation of bandwith.

Looks like the USB card/ROS USB has issues, which is the ROS version AND firmware version? (System > Routerboard Firmware versions listed)

What’s CPU load when doing this test?

Wouldn’t it be easier (and more optimal) to connect a second switch to the 2011 LAN ports?

The firmware version is the latest: 3.33
And yes probably adding a switch would fix the problems inmediately, but I’m only using 5 out of 10 ports of the AP, so why bought another 5ports switch(If thers no solution I probably will bought one, but I want to try all possibilities first).
And the CPU Load never gets exceeds a 6-7% when doing the test.