SV9100 Dropped Calls

[HoosierPapa]

Hi All,
I am troubleshooting reports of dropped calls on a SV9100. When I go through the logs, the examples I found look like regular Disco from receiving signal from carrier, Cause (16). I did find the below Layer 2 error message. I am not sure if it is the Carrier or the NEC causing. Is it indicating a D-channel drop? I lean towards carrier, but may be biased. Anyone familiar with decoding?

===== << 05/19, 16:04 >> =====

iUnitITSU::upUnitMessage(Slot=2) Layer 2 Error Report (27H:0BH:03H:01H:01H:05H)
== 19/MAY/2023, 16:4:7 ==
*(EVENT),ID:00000004H,P1:0002000BH,P2:00000000H,P3:118A3F74H
DATA[2] 22H to 27H and 81H: Clear ISDN selector

 

[CoralTech]

If disco is from carrier they are telling you to disconnect the call. Is this a traditional PRI or an IAD like off an Adtran or something?

 

[HoosierPapa]

I am not onsite but I am 95% certain it is off of an AdTran or similar equipment from talking to the onsite. I should clarify that the message in the post is separate from the dropped call examples I received. There are random times of the day and overnight that message pops off and looks unrelated to any call.