What is the cause of rlf due to "PDCP UL release"?

[dozman]

Hello, everyone.
‘PDCP UL release’ is seen in LTE log during data test. What is the cause of the message?

Test Condition

• ENDC option 3x : Split bearer

Test Scenario

1. Attach UE
2. Pump TCP DL
3. Data transfer well for about 60 seconds. (LTE : 100Mbps / NR : 300Mbps)
4. Data does not flow after 60 seconds, and RLF occurs after about 10 seconds.