Reconfiguration failure

Hi experts
I have an NSA test case for bands b3 and n78 but it is giving me a reconfigurationFailure error. After RRC Connection reconfiguration the UE sends lot of preambles to LTE and fails to add the NR cell. I see from the UE log file that there is an event “EVENT_nr5G_RRC_HO_STARTED” (as marked in red) but the source phy cell ID has a different value from the actual LTE cell where the UE was registered. I do not have much practical experience so I would appreciate any help on this. Could you please advice me what are the possible reasons for this problem and where should I look at in order to solve it.

Reconfiguration failure always happens whenever network send IE not supported by UE … please check b3+n78 combo supported by that UE or not in ue capability information

Thanks for you reply. Yes, I had checked that and it is supported.

Are you trying to add sgnb addition?

In the event of reconfig failure, ue will trigger re-est procedure and re-est can happen to any cell (source cell or other LTE cell).
If it is during NR cell addition then u may check band combination as someone already mentioned, bearer securtiy config, pdcp config, etc.

Yes Sir!! that is the first goal. I have further tasks but need to make sure that the NR cell addition works properly

please see in RRC message pkts on high-level description of what UE is not liking and why reconfig validation is failing. Accordingly, we can debug this.

As others have mentioned, UE capability is the first thing to consider specially for b3 band.
Next depending on the vendor, you may need to check the external cell definition (Huawei) and LCRID (Nokia). Also consider checking X2 config and if ANR is enabled or not.

Thanks for the time you invested in replying. I have checked the bands supported by the UE and are correct. Will check the other aspects you mentioned.

What is the first RRC message that UE sent after receiving RRC Reconfiguration message?

Is it RRC connection Re-establishment Request or SCG Failure Information? And what is the cause mentioned in it?

The message that UE sends is RRC connection re-establishment request, and the cause is reconfigurationFailure.
Thank you so much for your time

Can you share the content of the RRC_CONN_RECFG?