The Polycom phones have a known bug: only ring types 1-13 and 15 work correctly.
When using other ring types the following issues occur:

  • phones route the calls to voicemail after 1 ring
  • calls through Virtual Extensions won't go to voicemail
  • logs show the phone responds with a '302 moved temporarily' within 2-3 seconds of the INVITE
  • phones ring endlessly & never go to voicemail
  • phones ring more than they should
  • phones ring fewer rings then set up

There is no way to fix corrupted ring types (14, 16 and above), unfortunately.
Advise the customer to use the ring types 1-13 and 15.

If that does not resolve the issue, SIP ALG is likely the culprit. Please check the network for SIP ALG and disable if possible: How To Detect SIP ALG

_____________________________________________________________________________________

There is a Splash ring tone (#10) that is also present on the Yealink phones, however it is only similar to the Poly/Polycom Splash ring tone in two areas. They sound relatively the same and both only ring once.

Aside from those two items, the Yealink Splash ring tone does not affect any of the phones normal operations.

At this time, the only resolution is to avoid using the Splash ring tone on both Yealink and Poly/Polycom phones.