0 hits in search results

[rg-software]

I installed the Linux Docker image of SIST2, made it running (shows v3.4.2-SQLite). Tried to index a couple of small collections in SQLite mode, works fine. Next, indexed a larger collection (around 800,000 files), and now whatever I type in the search box, the system produces zero hits. When the search box is empty, I see the files, so the collection seems to be indexed fine. "Filter path" button also shows all the paths correctly. Even if I uncheck the large collection and leave only the small collection, no search results pop up.

Is there anything I can do to diagnose the issue? I don't see anything relevant in frontent-default.log, for example.