This is the complete log..
Time of Change Old Channel New Channel Old Power New Power Reason
-------------- ----------- ----------- --------- --------- ------
2015-12-15 16:49:58 13 13- 21 21 NO40INT
2015-12-15 15:55:34 13 13- 21 21 NO40INT
2015-12-15 14:25:39 13 13- 21 21 NO40INT
2015-12-15 13:36:13 13 13- 21 21 NO40INT
2015-12-15 13:10:58 13 13- 21 21 NO40INT
2015-12-15 11:57:44 13 13- 21 21 NO40INT
2015-12-15 10:45:44 13 13- 21 21 NO40INT
2015-12-15 10:02:06 13 13- 21 21 NO40INT
2015-12-15 09:12:50 13 13- 21 21 NO40INT
2015-12-15 06:23:02 13 13- 21 21 NO40INT
2015-12-15 04:39:42 13 13- 21 21 NO40INT
2015-12-15 03:37:12 13 13- 21 21 NO40INT
2015-12-15 02:44:22 13 13- 21 21 NO40INT
2015-12-15 01:40:32 13 13- 21 21 NO40INT
2015-12-15 01:05:23 13 13- 21 21 NO40INT
2015-12-14 23:49:21 13 13- 21 21 NO40INT
2015-12-14 20:31:41 13 13- 21 21 NO40INT
2015-12-14 13:02:42 9 13- 21 21 INV
2015-12-14 13:02:42 9 9 21 21 40INT
2015-12-14 12:42:31 9+ 9+ Max 21 P-
As you can see it shows 16.49 on December 15th.
I've just got in now and re-run the log, (as above) and it still shows the same, and doesn't register here as being on Ch1, which it still is.
And, as you suggested recently, i have set wide channels to 5GHZ only.
Also...
Just spotted this...
Minimum Transmit Power :30
Maximum Transmit Power :127
Band Steering Mode :disable
Client Aware :enable
This is the Arm configuration log.
I have ARM set to ... min 15 and max to max, for both bands.