weird asymmetric ping nv2

I’ve upgraded AP - SXT sa5 6.45b6 and client RB411+802.11n to 6.44.2 and what I see is

ping from AP to client
sent=20 received=20 packet-loss=0% min-rtt=2ms avg-rtt=4ms max-rtt=31ms

and return from client to AP\

sent=20 received=20 packet-loss=0% min-rtt=2ms avg-rtt=13ms max-rtt=37ms

Nv2 protocol, 1ms TDMA period size, dynamic downlink 70

shouldn’t ping be more or less equal both sides?

When switched to 802.11, avg both sides is 0ms, on nstreme also look much better and equal both sides.
SNR -73 dbm with 135/135 rate (long GI), CCQ 93/99

Has this been in the previous version?