PCU socket not connected, dropping message

Dear baseband developers team,   I built home gsm network with Osmo-stp-msc-hlr-bsc-bts, osmo-trx limeSDR.   I managed and registered phones. I did send sms between each other. However when i decided to make a call — i noticed following message in terminal: «PCU socket not connected, dropping message».   I searched on Osmocom web site and it is said that pcu socket is involved in GPRS things (i.e. in internet). Therefore why does such message appears when i try to make simple call between two mobiles — it has nothing to do with GPRS…   And what would you advise me how to resolve this ?   P.S. initially when i was about to start osmo-bts-trx i got message «PCU L1 socket failed» and i just renamed the pcu_bts file to some other name and osmo-bts-trx started.   Thank you so much for your kind reply.   Best regards             -- Mario Lucas