I have seen this issue recently, and directly after upgrading from the 12.28.1 to 14.32 version, but with a small twist.
We are using Yealink VoIP phones and at some places a PC is connected via the phone to the MS225 switch.
Now only in these setups the VoIP phone seems to loose connectivity with the SIP server on the Voice VLAN.
The PC connection seems to remain in tact, I started looking into this issue.
Also - no issues found when an PC is connected directly to the switch, or the VoIP phone is connected "solo" to the port.
Did the rollback fix the issue for you?