Assertion failure in du_processor_impl.cpp:486 when UE disconnects Environment

[vilian3688]

Environment

• srsRAN Project version: 24.04
• Platform: Ubuntu 22.04
• Deployment: gNB + 5GC from srsRAN Project
• Device under test: 5G module (e.g., RM500U-CN 5G HAT)
• Core network: srsRAN 5GC

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Description

When using my 5G module to connect to the srsRAN 24.04 gNB and 5GC, the UE can successfully attach and access the external network.
However, occasionally the gNB terminates with the following assertion failure:

/home/ubuntu/srsRAN_Project-release_24_04/lib/cu_cp/du_processor/du_processor_impl.cpp:486:
void srsran::srs_cu_cp::du_processor_impl::send_ngap_ue_context_release_request(srsran::srs_cu_cp::ue_index_t, srsran::ngap_cause_t):
Assertion `ue != nullptr' failed - ue=0: Could not find DU UE.
Aborted

After this happens, the gNB process stops, and the 5G module loses connection with the core network.
Interestingly, this issue does not occur when testing with a Redmi 5G smartphone — the phone can attach and detach repeatedly without triggering the assertion.

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Question

Could you please explain what this assertion (ue != nullptr in send_ngap_ue_context_release_request) means?
It seems that the gNB CU-CP failed to find a corresponding DU UE when sending a context release request, but I’d like to confirm whether this interpretation is correct and what might cause it.