Hello Victor-
The switches in this envirnoment are Cisco, and the issue occurs across multiple switches in the buildings. I cannot say with 100% accuracy that none of the computers are behind a VoIP phone, but many of them are not.
Port config follows:
switchport access vlan XX
switchport mode access
switchport voice vlan XXX
no logging event link-status
power inline auto max 7700
srr-queue bandwidth share 10 10 60 20
queue-set 2
priority-queue out
authentication event server dead action reinitialize vlan XX
authentication event server dead action authorize voice
authentication host-mode multi-auth
authentication open
authentication order dot1x mab
authentication priority dot1x mab
authentication port-control auto
authentication periodic
authentication timer reauthenticate server
mab
no snmp trap link-status
mls qos cos 2
mls qos trust cos
dot1x pae authenticator
dot1x timeout server-timeout 30
dot1x timeout tx-period 10
dot1x max-req 3
dot1x max-reauth-req 3
spanning-tree portfast
spanning-tree bpduguard enable