Queue issue - not all consultant phones ring

I tried it on a couple of releases of asterisk and system behaves the same. Currently
I have defined 5 different queues, each has a different priority. In general all consultants are assigned to all queues. Ring strategy is ringall. Call limit is 5, busylimit is 1, limitonpeers=yes.
Sometimes 10 consultants are available, but on an incoming call only 2 Eye-Beams ring, but most of the time all ring OK. Customer demands that I solve this issue.
thanks in advance