REAL UE drops PDU session after 15-20 minutes

We are running free5gc 3.2.1
We have E/// radio and a HTC Desire UE
It registers and establishes a PDU session … You can then browse etc but after 15-20 it drops the pdu session with error below…
pcap and free5gc amf and smf logs attached

time=“2022-10-05T22:54:56Z” level=info msg=“Handle Error Indication: RAN_UE_NGAP_ID:&{18207} AMF_UE_NGAP_ID:” category=NGAP component=AMF ran_addr=“” (66.0 KB)