Simu5g - Error in handover enabled 5G communication

[sh.t w]

Hi!

I am trying to implement a handover scenario with simu5g and have used three base stations and 15-user equipment. I set the carrier frequency to be 5GHz and the number of bands = 25. The system works fine but sometimes, it just end up in either of the two errors below. 

<!> H-ARQ TX: fb is not for the pdu in this unit, maybe the addressed one was dropped -- in module (NRMacUe) AgentNetwork_NR.ue12[1].cellularNic.nrMac (id=636), at t=331.056s, event #21243022

<!> (omnetpp::cArray): addAt(): Position 15 already used -- in module (UmRxEntity) AgentNetwork_NR.gnb2.cellularNic.rlc.UmRxEntity Lcid: 1 (id=1204), at t=142.111s, event #14340732

I am a bit confused as this doesn't always happen. Have anyone encountered this error before or have any idea how to prevent this from happening?

Thank you!

[sh.t w]