PSR-310 occasional no audio on certain talkgroups

[V_A_R_I_A_B_L_E]

I have observed this behavior only while monitoring a particular scan list (#4, which contains talkgroups from Multhomah County Sheriff's Office, all of the other scan lists containing talkgroups on this TRS have not presented this issue). Does anyone have any idea what's going on here?

Video of the behavior:
GRECOM PSR-310 Scanner: Issue with no audio while trunking - YouTube

TRS in question: Portland Public Safety Radio System
Portland Public Safety Radio System Trunking System, Portland, Multi-State - Scanner Frequencies