btest from v5.22 to v6rc8 shows bad speed(1mbit-to20mbit/s)

despite the real throughoutput, when I do it from v5.22 to v5.22 is 39mbit/s stable…
What is the problem?

please describe your test setup, and all the test settings. what devices are you running it on?

I just find out where is problem. This happens only in evening times when a lot of people is connected. Routers despite that their shows max. 60% cpu are not capable ro run btest and speed is from 1mbit/s..but if I do test to main router(which is much more powerfull) everything is fine…
How to best check router resources…because that showed in cpu usage are not objective…

HDeleted because not related.

is possible to make test from mikrotik client to netio server?
I have situation:
mk1-wireless-mk2-wireless-mk3-wireless-mk4
and automatic scripts that reguralry check throughoutput between separate wireless, to see if somwhere is throughoutput speed(to be able in time change frequency…)…