Timeout on non-critical invite transaction

Hello,

Our Asterisk server is working well but sometimes we get the following warning in the CLI:

WARNING[22148]: chan_sip.c:4109 retrans_pkt: Timeout on 6185a510c8ecdc5cdfddcebc583642dd on non-critical invite transaction.

What are the possible cause(s) of this warning and would you suggest anything to get rid of it if possible?

Thanks