One information for all users who want to confirm the setting mentioned by Daniel:
After restart of seafile server, you should take a look at the following log file:
logs/elasticsearch.log
on line 6 there is the follwing conent:
JVM arguments [-Xms1g, -Xmx1g, -XX:-AssumeMP, -XX:+Use ...
If you search for -Dlog4j2.formatMsgNoLookups=true and it appears there, the fix is working for you (Elasticsearch has been started with this setting).
Maybe this can help someone.