VP59 Teams issue with incoming sound

[btpuk]

I've created tickets in Yealink portal with no success, so am reaching out to the forums.
I have a VP59 Teams handset. The inbound audio is really odd, it either doesn't exist or the sound is stretched and delayed. I ran several tests and sometimes the sound took 5 or 6 seconds to start, and it was slow and robotic. There is no problem with people hearing me, and no video issues either.
The phone is powered from a PoE switch and I took the VP59 home last week, where it worked absolutely fine on a Netgear GS110TP mini switch. I brought it back to the office and connected it to a different switch, a GS48TP, and yesterday the phone worked perfectly.
Today it's reverted back to me not being able to hear any voice and it's really driving me mad.
I've ordered a power supply which is out of stock so while I wait I wondered if anyone else had experienced this, or had any suggestions? It's a very expensive paperweight at the moment!
Thanks