Filestash developer here. It's the first time I hear about anyone having reliability issue with Filestash, can you provide more details about the issues you've run into as without specific examples, it’s difficult to identify and fix any potential problem.

Regarding full-text search: There are multiple approaches. One such implementation is open-sourced and available here: https://github.com/mickael-kerjean/filestash/tree/master/server/plugin/plg_search_sqlitefts

The default search is indeed a recursive because not everyone fully understand that creating a full text search index come with downloading potentially a lot of data and if you use a storage like S3 which charge a lot for bandwidth could cause some large billing issues ....

Might check out Paperless-ngx. I know it has full text search. It OCRs everything you put in it. Not sure about integrating it with Wordpress though.

Why do you need it to be in a Wordpress page? I can’t quite see what you’re trying to accomplish.

There a handful of approaches that may be helpful for this. I don't want to make any assumptions on what you've tried, yet, though. Would you mind clarifying what you've given a go at, so that we don't offer something that doesn't do what you're looking for?