Snom phones rebooting while connected to Netgear PoE switch

Greetings,

I have a GS752TPS switch to which different devices including Snom IP phones are connected. The switch has a data VLAN and a voice VLAN (1 and 20 respectively). The ports for VLAN 20 to which the Snom phones connect are tagged. Most of the time, everything is working fine; sometimes however, different phones, get stuck in rebooting. (This while either phones are working completely fine, even if they are rebooted at that time)

The error message I get is:

No Network Policy, LLDP fallback to VLAN reset. Rebooting...

Some additional information:

- The firmware version of the PoE switch is: 5.3.0.6

- The switch is connected to a Sonicwall which is the DHCP server. (Plenty of addresses available in the scope)

- We have another similar switch GS752TPS on a different floor which is connected as well to the Sonicwall, but while is has identical configuration, the phones connected to it never had any issues.

- I bypassed the PoE switch with 2 phones that were not working, connected them directly to the sonicwall using a simple

unmanaged switch and they got IPs.

Is there something that could be recommended for this?

Please let me know what additional information I can provide for this.

Thanks