MAC reject message in syslog


I am not new to this list, but did several years only read - not write anything.

Now i have a problem on a new Leap15.3 installation.
In the syslog are sometimes lines like the following:

Sep 27 00:29:30 mail kernel: eth1_mac REJECT IN=eth1 OUT= MAC= SRC= DST= LEN=277 TOS=0x00 PREC=0x00 TTL=64 ID=172 DF PROTO=UDP SPT=138 DPT=138 LEN=257

This seems to me a message from the samba area, but dont know, why this comes up sometimes.

Does anyone have any idea?

Many thanks in advance for your ideas.