I've been experiencing this in both stable and snapshot releases for the MR8300.
A few hours after a reboot the wifi performance degrades over that period and the throughput goes down from 10MB/sec to 2.3MB/sec maximum. This is transferring data between mobile and laptop in the same location every time. If I reboot the router and try again, the performance goes back to the maximum.
Wondering if anyone has experienced a similar issue.
I checked the channels and both devices are using 5GHz and I also checked for conflicting traffic and mine is the only one using channel 44, other SSIDs are using 36.