Today I found out that AP-15 in the following mesh configuration was the source of the problem:
No network connection to AP-15 and it's child APs (AP-19, A-17, B-18, B-14,A-16),
when testing links with "child" (AP-19) and "parent"(AP-21) APs "Error: Cannot get
stats from the destination ap" message but it sends and receives packets to and
from other neighbor APs.
After Hardware Reset on WLC web interface AP-15 functions normally.
Here is the mesh configuration:
=======================================================
|| AP Name [Hop Counter, Link SNR, Bridge Group Name] ||
=======================================================
[Sector 1]
----------
Central_AP-10[0,0,default]
|-AP-21[1,42,default]
|-AP-15[2,31,default]
|-AP-19[3,39,default]
|-A-17[4,37,default]
|-B-18[4,40,default]
|-B-14[4,39,default]
|-A-16[5,31,default]
|-AP-22[2,22,default]
|-AP_02-12[1,26,default]
|-AP_03-20[2,39,default]
----------------------------------------------------
Number of Mesh APs............................... 11
Number of RAPs................................... 1