Workstations in switchports that have a voice VLAN configured are getting addresses from the voice DHCP server

As the title suggests, I have workstations that get network connectivity through an Ethernet passthrough on Mitel 5330e phones. The switchports are regular access ports on our data VLAN, and we have the voice vlan configured with our voice VLAN. We have a helper address pointing to our workstation DHCP server on the workstation VLAN, the voice VLAN does not use a helper / relay as the phone controller serves out DHCP on broadcasts.

2 nights ago, we got calls from a handful of people in the building about not having network connectivity. We found out that those workstations had IP addresses from our voice subnet as opposed to our workstation subnet. If you do a release and renew, it will continue to grab a voice subnet address. The only way to get a workstation address is to remove the voice vlan from the affected port. Alternatively, if you give the workstation a static IP from the workstation subnet you will get connectivity, although not right away in most cases. I've had to do continuous pings to the gateway or some other network address for about 5 to 10 minutes before I'll start getting replies and connectivity will be restored.

There were no topology or configuration changes made to my knowledge. The only thing I discovered that I had thought was causing the issue was a device that was absolutely flooding the network with DHCP Discover messages. After removing the offending device I was hoping the issue would be resolved, but we're still seeing it.

For added background, we've been operating with the same configuration for 3 years and never had an issue. I feel like something had to have changed but I've run out of places to look in an attempt to track this down. I have Wireshark captures available in case anyone wants to look at them.