Netgear GS752TPP v3 and IP phone problem

Hello,

I got a problem with GS752TPPv3 and IP phones.

For some reasons, when we connect IP phone to this switch, the sound is bad. Also, we noticed, that it is dropping packets.

I noticed when I put a "dump"(unmanaged) switch between- everything works well.

I do not use any VLANS. I disabled LLDP-med.

I see, that the switch has some default configs for voice and phones with VLANS, but I can't delete anything.

I'm out of ideas what to do.

Maybe someone have any suggestions?