Please try the following:
Stop sphinxsearch and
echo "Start=No" >> /etc/init.d/sphinxsearch
1) Stop onlyofficeIndex. Stop processes: searchd, indexer.
2) Clean the folder /var/www/onlyoffice/Data/Index
3) Clear table in the db: webstudio_index
4) Start onlyofficeIndex
In fact, it shall re-launch the Indexation service. Contact us and inform of the results, please.