Yes, it is a limitation in SD Card performance and I fixed it using a SSD (Solid State Disk), but expect you can also use a HDD.
In summary:
My HA froze from time to time as did all connections of the Conbee II stick became unavailable from time to time. I found out that both issues had one thing in common, being the high CPU load (not to be mistaking with CPU Usage percentage) before or at the moment of the issue.
I found out that the high CPU load was caused by a high CPU IO Wait (as shown in the images). What basically happens is that your CPU is waiting for the read/write actions to finish. Currently I have a max IOWait of 2% (using an SSD), where this was 100% quite often and for longer times using a SD card.
Disclaimer: The reason for the load is/was not per se HA itself. I reduced the issue a little by limiting the frequency of logbook writes, which helped a little. I use several addons which can/could also very well be the reason of the amount of IO. I however wanted to keep them, so I decided to increase performance instead of lowering the IO.
So I am not saying my solution is the only or only right solution, it’s basically a tip for troubleshooting.
Resume
The first step I’d advice in troubleshooting not a respondong HA, is see if the CPU is obstructed in any way. By default the sensor platform ‘systemmonitor’ gives you all the tools but not IOWait. Therefor I created the commandline sensor shown above.