samba - Mar 2024 - smbd rejects all and any authentication attempts due to a corrupted "gencache.tdb"

I run smbd 4.18.8 inside a docker container via "smbd --foreground"
(see the attached config). Recently my server was abruptly
restarted due to a power outage. Upon the restart it was able to successfully
start the container, but the shares became inaccessible
due to smbd rejecting all authentication attempts. In the logs I found:

[2024/03/18 08:22:50.790021,  5] ../../source3/lib/gencache.c:89(gencache_init)
 Opening cache file at /var/cache/samba/gencache.tdb
[2024/03/18 08:22:50.790204,  1] ../../lib/tdb_wrap/tdb_wrap.c:65(tdb_wrap_log)
 tdb(/var/cache/samba/gencache.tdb):
tdb_mutex_open_ok[/var/cache/samba/gencache.tdb]: Mutex size changed from 458752
to 401408
 .Opening /var/cache/samba/gencache.tdb failed: Invalid argument
[2024/03/18 08:22:50.790473,  4] ../../source3/smbd/sec_ctx.c:443(pop_sec_ctx)
 pop_sec_ctx (0, 0) - sec_ctx_stack_ndx = 0
[2024/03/18 08:22:50.790538,  3]
../../source3/smbd/smb2_server.c:3962(smbd_smb2_request_error_ex)
 smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_UNSUCCESSFUL] || at ../../source3/smbd/smb2_negprot.c:320

After I manually deleted "gencache.tdb" and restarted the container
all access was restored.

Why did not smbd discard the file?


[global]
server role = standalone server
log file = /dev/stdout
dns proxy = no  
passdb backend = smbpasswd
obey pam restrictions = yes
security = user
printcap name = /dev/null
load printers = no
dns proxy = no
wide links = yes
follow symlinks = yes
unix extensions = no
acl allow execute always = yes
vfs objects = catia fruit streams_xattr
fruit:model = TimeCapsule
fruit:aapl = yes
log level = 1
workgroup = WORKGROUP
server string = Samba Server
map to guest = Bad User
min protocol=SMB2
server string=Home Library
fruit:model=RackMac
fruit:metadata=stream
fruit:wipe_intentionally_left_blank_rfork=yes
fruit:delete_empty_adfiles=yes
disable netbios=yes

[Movies]
path=/shares/Movies
create mask=0644
directory mask=0755
writable=yes
browseable=yes
public=yes
force user=guest