Nighthawk M6 Pro MR6450 Flaky Internet over WiFi

I am using a Nighthawk M6 Pro (model number MR6450, FW version NTGX65_12.01.54.00) connected to an EE network over 5G, in performance mode with battery out and original power supply. The WiFi is configured as Dual mode 2.4+5GHz (WiFi 6, not 6E), the SSIDs are set to have the same name. It used to work perfectly fine for a month, then I started having internet issues when using WiFi. The display shows 4 bars and 5G, a speed test showing 300Mbps+ at times. However, there are numerous times when the internet connection becomes flaky and is dropping, for minutes at a time. Then it starts working again for a few minutes (albeit slow internet connection), then it drops again. Both WiFi bands are set to auto and checked with a WiFi analyzer app that there are no big interferences in the area. The issue is non-existent when I am plugged to the Ethernet port. Therefore, I suspect something is wrong with the WiFi and not with the 5G connection. Has this happened to anybody before and is there a known issue regarding this? Thank you!