On Linksys WRT1900ACS (and possibly other devices using marvel 88W8864 WiFi), WiFi connectivity is intermittently unreliable. On my Galaxy S10e smartphone, the symptom is that the device reports being connected to WiFi, but when trying to load a web page, it takes forever. The device switches to cellular connectivity after some time, and reconnect to WiFi (possibly on the other band) and then it works for a while.
As a couple users have reported, it is necessary to disable TX AMSDU to fix this bug.
This can be accomplished by issuing the following commands:
Also having this issue with WRT1900ACS v1 on both 21.02.0 and 21.02.1. I've noticed this being a problem only on android devices. On both windows PCs and IOS wifi seems stable, multiple android devices will hangup/loose connection very frequently.