Saving imputation fails for one user only

Good morning,
I'm from Hexis we had a training on projeqtor few weeks ago and now we start to use it.
One of my colleague, who has the same configuration and rights as me has an issue when trying to save imputation.
He clicks on the floppy disk icon to save, the page seems to do something but there is no "imputation saved" pop-up.
Every body else works OK.

Here is what happens in the logs : 2026-06-08 09:22:15.367 ===== TRACE ===== [12] WARNING - Left work not retrieved from screen
2026-06-08 09:22:15.367 ===== TRACE ===== [12] - Maybe max_input_vars is too small in php.ini (actual value is 4000)
2026-06-08 09:22:15.368 ***** ERROR ***** [V12.5.0] [12] ERROR *****
2026-06-08 09:22:15.368 ***** ERROR ***** [V12.5.0] [12] on file 'E:\projeqtor\tool\saveImputation.php' at line (40)
2026-06-08 09:22:15.368 ***** ERROR ***** [V12.5.0] [12] cause = Passing E_USER_ERROR to trigger_error() is deprecated since 8.4, throw an exception or call exit with a string message instead
Any idea what could be wrong ? It's weird since everybody else works fine...