Have searched and read around for hours without success.
Maybe it's a known issue or easy to give a hint by someone with experience.
This is a fully updated Centos7, kernel-3.10.0-1160.45.1.el7.x86_64, samba-4.10.16-15.el7_9.x86_64
Happens 2-5 times a day, 100+ PDC joined Win10 Pro (21H1), maxprotocol NT1.
Trace is identical for several workstations throughout the day:
[2021/11/09 14:04:40.801186, 0] ../../lib/util/fault.c:79(fault_report)
===============================================================
[2021/11/09 14:04:40.810527, 0] ../../lib/util/fault.c:80(fault_report)
INTERNAL ERROR: Signal 11 in pid 12147 (4.10.16)
If you are running a recent Samba version, and if you think this problem is not yet fixed in the latest versions, please consider reporting this bug, see https://wiki.samba.org/index.php/Bug_Reporting
[2021/11/09 14:04:40.810584, 0] ../../lib/util/fault.c:86(fault_report)
===============================================================
[2021/11/09 14:04:40.810611, 0] ../../source3/lib/util.c:824(smb_panic_s3)
PANIC (pid 12147): internal error
[2021/11/09 14:04:40.877304, 0] ../../lib/util/fault.c:265(log_stack_trace)
BACKTRACE: 44 stack frames:
#0 /lib64/libsamba-util.so.0(log_stack_trace+0x2f) [0x7fae07a6700f]
#1 /lib64/libsmbconf.so.0(smb_panic_s3+0x18) [0x7fae0725ee88]
#2 /lib64/libsamba-util.so.0(smb_panic+0x2d) [0x7fae07a6711d]
#3 /lib64/libsamba-util.so.0(+0x1a37e) [0x7fae07a6737e]
#4 /lib64/libpthread.so.0(+0xf630) [0x7fadf873b630]
#5 /lib64/libpthread.so.0(pthread_mutex_lock+0) [0x7fadf8735d00]
#6 /usr/lib64/samba/libsmbd-base-samba4.so(+0x15e3c9) [0x7fae076213c9]
#7 /usr/lib64/samba/libsmbd-base-samba4.so(smbd_lock_socket+0x9) [0x7fae07621da9]
#8 /usr/lib64/samba/libsmbd-base-samba4.so(srv_send_smb+0x45) [0x7fae07623f35]
#9 /usr/lib64/samba/libsmbd-base-samba4.so(+0xff126) [0x7fae075c2126]
#10 /usr/lib64/samba/libsmbd-base-samba4.so(+0xff335) [0x7fae075c2335]
#11 /usr/lib64/samba/libsmbd-base-samba4.so(change_notify_reply+0x79) [0x7fae07667a69]
#12 /usr/lib64/samba/libsmbd-base-samba4.so(remove_pending_change_notify_requests_by_fid+0x33) [0x7fae07668773]
#13 /usr/lib64/samba/libsmbd-base-samba4.so(close_file+0x398) [0x7fae0760b418]
#14 /usr/lib64/samba/libsmbd-base-samba4.so(file_close_conn+0x5a) [0x7fae075a5f0a]
#15 /usr/lib64/samba/libsmbd-base-samba4.so(close_cnum+0x5f) [0x7fae0762a0af]
#16 /usr/lib64/samba/libsmbd-base-samba4.so(smbXsrv_tcon_disconnect+0x74) [0x7fae0765a2c4]
#17 /usr/lib64/samba/libsmbd-base-samba4.so(+0x1975f2) [0x7fae0765a5f2]
#18 /usr/lib64/samba/libdbwrap-samba4.so(+0x524c) [0x7fae05bee24c]
#19 /usr/lib64/samba/libdbwrap-samba4.so(+0x53ea) [0x7fae05bee3ea]
#20 /usr/lib64/samba/libdbwrap-samba4.so(dbwrap_traverse+0xa) [0x7fae05bec8da]
#21 /usr/lib64/samba/libsmbd-base-samba4.so(+0x1961c0) [0x7fae076591c0]
#22 /usr/lib64/samba/libsmbd-base-samba4.so(smb1srv_tcon_disconnect_all+0xf) [0x7fae0765a6df]
#23 /usr/lib64/samba/libsmbd-base-samba4.so(+0x19a684) [0x7fae0765d684]
#24 /usr/lib64/samba/libsmbd-base-samba4.so(smbd_reinit_after_fork+0) [0x7fae0765db20]
#25 /usr/lib64/samba/libsmbd-shim-samba4.so(exit_server_cleanly+0x14) [0x7fae01b8db14]
#26 /usr/lib64/samba/libsmbd-base-samba4.so(+0x16332a) [0x7fae0762632a]
#27 /lib64/libtevent.so.0(tevent_common_invoke_fd_handler+0x83) [0x7fadf851fb13]
#28 /lib64/libtevent.so.0(+0xd087) [0x7fadf8526087]
#29 /lib64/libtevent.so.0(+0xb057) [0x7fadf8524057]
#30 /lib64/libtevent.so.0(_tevent_loop_once+0xbd) [0x7fadf851f25d]
#31 /lib64/libtevent.so.0(tevent_common_loop_wait+0x1b) [0x7fadf851f4bb]
#32 /lib64/libtevent.so.0(+0xaff7) [0x7fadf8523ff7]
#33 /usr/lib64/samba/libsmbd-base-samba4.so(smbd_process+0x6b1) [0x7fae07627531]
#34 /usr/sbin/smbd(+0xb2e8) [0x5645dffe02e8]
#35 /lib64/libtevent.so.0(tevent_common_invoke_fd_handler+0x83) [0x7fadf851fb13]
#36 /lib64/libtevent.so.0(+0xd087) [0x7fadf8526087]
#37 /lib64/libtevent.so.0(+0xb057) [0x7fadf8524057]
#38 /lib64/libtevent.so.0(_tevent_loop_once+0xbd) [0x7fadf851f25d]
#39 /lib64/libtevent.so.0(tevent_common_loop_wait+0x1b) [0x7fadf851f4bb]
#40 /lib64/libtevent.so.0(+0xaff7) [0x7fadf8523ff7]
#41 /usr/sbin/smbd(main+0x1af8) [0x5645dffdda98]
#42 /lib64/libc.so.6(__libc_start_main+0xf5) [0x7fadf7f63555]
#43 /usr/sbin/smbd(+0x8e34) [0x5645dffdde34]
[2021/11/09 14:04:40.877875, 0] ../../source3/lib/dumpcore.c:315(dump_core)
dumping core in /var/log/samba/cores/smbd
