docs: Adds troubleshooting section for fulltextsearch

README.md

@@ -286,3 +286,11 @@ And you can populate the index manually and check if any errors occur:
 ```
 abra app cmd <domain> app run_occ '"fulltextsearch:index"'
 ```
+
+### Troubleshooting fulltextsearch
+
+The fulltextsearch plugin might be stuck with this error: "Index is already running". In that case the following command can get things runing again:
+
+```
+abra app run <domain> db /bin/sh -- -c 'echo "delete from oc_fulltextsearch_ticks;" | mariadb -u root -p$(cat /run/secrets/db_root_password) nextcloud'
+```