B5 / B5c high jitter

Hi Mimosa community,
we have several Mimosa B5 and B5c radios in our network. All radio links with mimosa have high jitter.
Latency is normally good except in a few seconds for minute where ping goes randomly high, up to 200ms, 400ms or 1100ms.
This causes problems to voip users and videogamers.
Radios works in noise environment, unfortunately is a common situation for us.
Upgrading to 1.3.1 and choosing more clean frequency help me but not solve definitly.

How can I solve this issue?
Thanks.