Phones crash using VM

[Impress1]

We have a yeastar P550 and 3 T48S phones. All are at latest firmware vers. 66.86.0.15
If you try to retrieve voicemail messages the phones crash to bluescreen then reboots welcome message. The PBX shows the call/VM is still in use or active.

We can usually login to VM and listen to one message, but the phone will crash at any point during use of the VM retrieval process.
We follow prompts to delete the message played and the phone crashes.
It appears to usually crash most on deleting a message.
We can recreate the issue also by login to VM and try to play old messages and it will crash at that moment too.

YeaStar support claims the PBX cannot reboot phones. I think it can.

This happens on all the phones we have; I think it’s a configure issue maybe?
Thanks Jeff-