Global search suddenly stopped working

After loading a lot of new data in our DataGerry instance, we lost the ability to search.
Our datagerry log files shows the following error message:
[Search Framework Rest]: invalid literal for int() with base 10: ‘SearchString’ (search_routes.py)

It seems that a python script is trying to convert our SearchString into an integer which of course fails. Any idea where I can investigate the source of this error ?