Hi, I have two problems with my router AX50 with last firmware.

Basic information:

ISP 300/150mbps - optical

Test devices:

NB Dell Latitude 5411 with last driver version - 21.06.2022, Wifi card - Intel Wifi 6 AX201 160MHz, default settings on 802.11.AX mode

Mobile phone Samsung S21 with last FW (reference good device).

Mobile phone Xiaomi 10T with last FW

1. Some device has slow download speed (10-13Mbps) and good upload (150Mpbs). On Samsung S21 is everything good download speed 300/150. On Xioami 10T is slow download speed - 13/150Mbps. On NB DELL is speed 13/76Mbps:

Other devices in home working well +-300/150Mbps (other mobile phone, NB etc...) only these 2 devices working bad. 

I try many many settings, Wifi from auto channel/width to manual, disable QOS, disable VMM, disable 2,4GHz, factory default... but without any success. I have scanned the entire netstumbler network and there are no other networks on my channels. Do you have any advices?

2. Several times a day the Wifi signal is completely lost. The device won't ping and it usually helps to wait a while or reconnect (when I scan the freqency bandwidth my network disappears (in SW Netstubmler or NetAnalyzer)). There is no information in the LOG of the device e.g. reboot. 

Can you give me some advices?