In my case, when I try to establish dedicated bearer and modify another bearer, I don’t receive modification confirm. So ERAB Setup procedure and ERAB Modification procedure collide with each other. I couldn’t find why.
The SCG Release due to MCG Mobility is because the UE HO failure happens at the 4G side as indicated by the message “UEContextReleaseRequest” sent from eNB to the EPC at 23:45:51.332, so the sequence of messages completed by the EPC reply and then the SCG release.
In between all these messages the 5G BTS sent the message “SgNBActivityNotification” to the 4G BTS declaring that UE is inactive, however the 4G BTS ignored this message and completed what it was started for the HO failures as the release due to HO fail is already sent to the core.