Also noticed what could be a bug, but not sure if introduced in 4.4.5 or a prior release.
Changed the amount of days to display/keep to their mximums (not sure if any other values create the issue)
View attachment 46535
Once I did that, the bandwidth test would not run/give results regardless of which binary (Built-In or External) I used, even if I changed the values back to what they originally were - the test would still fail to run. I had to reselect the preferred server again to fix it.
Did you see any error message when it fails to run? Can you check if the Preferred servers for interfaces values are still intact once you make changes on the number of days to keep?
You can also verify the external binary by replace the server_id with your preferred server id and see if it can run.
/jffs/addons/spdmerlin.d/ookla/speedtest -s <server_id> --accept-license --accept-gdpr