[Borgbackup] Regular backup strange behavior (stuck)

[Bzzzz]

debian : bookworm
borg   : 1.2.7 (from pip)
repo   : mounted on the client with nfs
	 (readable from another console,
	  so not a network PB)
========================================

Hi list,

One machine normally takes something like 30'~35' to backup, however
today borg is up for largely more than 1 hour !?
start time : 21:01:29
this time  : 22:45:09

The console where my script was launched shows the usual list of
modified files, no recap so it is assumed to be still running, there
is no error message at all and the last repo file shows one created file
with the last access 2' after backup was started and that is all :
$ sudo stat /NFS/BORG/data/3/3992
  File: /NFS/BORG/data/3/3992
  Size: 147182858 	Blocks: 287480     IO Block: 131072 regular
file Device: 0,87	Inode: 112984077   Links: 1
Access: (0600/-rw-------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2024-01-25 21:02:26.104944402 +0100
Modify: 2024-01-25 21:03:07.375370789 +0100
Change: 2024-01-25 21:03:07.375370789 +0100
 Birth: -

I already tried to kill borg and relaunch it but with the same result,
it stays stuck on the last (?) modified file and nothing else occurs.

What could be wrong ?

Jean-Yves