@yves
I'd be interested to see if the same issue occurs on the latest version of FusionAuth. There's 4-5 mentions of Elasticsearch in the release notes between 1.34.0 and 1.45.3, but none of them appear to address what you are seeing.
As mentioned above, also searching directly via id for example fails.
Sorry, I missed that. Are you saying when you search using the ids method (described here under the heading Search for Users by Id) it doesn't find these users? Because that search should go directly to the database and not through ES at all.
It's all a bit suboptimal.
Off topic, but please consider adding your voice to this issue which might help with your schema changes.