A fix for this issue may be too much load on the voice server; it could be as simple as reducing the codec quality in terms of a quick and dirty fix.
At least until something can be done to fix the underlying issue; besides, voice comms don't need to be as clean as they are.
The encoder settings are definitely set to high quality / bit-rate; it's like listening to FM when all we really need is Shortwave or AM.
By contrast even SiriusXM Radio's music channels doesn't sound as good as the comms in Arma III and we don't really need to broadcast music over side chat do we? lol