Hi
We have had a very similar issue. Running approximately 60 MR52s across the enterprise. Tuning has been done manually for channels and power as found we could get a much better result than allowing the APs to manually complete this. Everything worked perfectly. my.meraki gave high download speeds consistently.
However after a few weeks to a month the usual report is poor performance and running a my.meraki speedtest which only tests bandwidth between the device and the AP shows a maximum speed of 20Mbs. We have tried to change the channels in use, power settings, channel width all to no avail. In some cases I have seen 0-1Mbs on the my.meraki test.
We have tried all the different Meraki firmware available and custom firmware, still to no avail. A ticket has been open with Meraki for months and still its in their "research and development section" with no solid answer forth coming.
I feel Meraki have really dropped the ball on this and they have had countless options to resolve it. I used to really believe in Meraki hardware, and while all devices have issues, the real key to customer service is how you deal with the problem. There is no way a retail shop would have got away with this fiasco.
We feel the Meraki devices have a hardware issue as I never saw these issues on MR33s or lower spec devices in the past. The symptom is a memory leak.
We also have a few MR56s we have installed and touch wood after weeks and weeks we have no issues at all so far.
These are affecting not only one office but multiple offices around as well, so it is not an environmental issue either as all offices are different types, some very isolated to the outside world so no chance of interference.
I have spent hours and hours with Meraki on this one and sent countless packet capture logs we had to acquire an Apple MAC so we could obtain the details they required.
However as of today I have just had to reboot 6 APs to resolve issues for clients and suspect I will need to do more.
I have even raised to Meraki they need to own this issue and arrange a scheduled staggered reboot to provide a stop gap for us. However that was met with a solid no. Also there is no uptime in the dashboard which would help predict the issue and be proactive. Meraki have uptime on their dashboard but customers dont...go figure...
We have also been told we are the only ones experiencing this issue, which I know is not the case, however this is the most recent post I have seen concerning these devices.
All I can suggest is push Meraki hard. There are issues as we are experiencing them as well.
Cheers
Michael