Started noticing these in the Samba logs now on a couple of our servers:
[2021/10/07 23:26:02.557294, 0] ../../libcli/smb/smb2_signing.c:433(smb2_signing_calc_signature)
smb2_signing_calc_signature: opcode msg_id == 0
[2021/10/07 23:26:02.557342, 0] ../../libcli/smb/smb2_signing.c:705(smb2_signing_check_pdu)
smb2_signing_check_pdu: smb2_signing_calc_signature(sign_algo_id=1) - NT_STATUS_INTERNAL_ERROR
Most users seems to be able to login just fine so I'm assuming this is some specific client doing something strange?
*** This bug has been marked as a duplicate of bug 14855 ***