Search filter based on collection returns nothing

[Pooya-Oladazimi]

Describe the bug
search filter based on a collection returns nothing although the result exists.

To Reproduce
call: /api/search?q=assay&start=0&groupField=iri&rows=20&schema=collection&classification=NFDI4CHEM

equivalent in ols3: https://service.tib.eu/ts4tib/api/search?q=assay&start=0&groupField=iri&rows=20&schema=collection&classification=NFDI4CHEM

Additional context
Besides the empty result issue, facet data looks funny:

[giraygi]

The call in the description work in prod1 but not in prod2
When I change the call as api/search?q=assay&schemas=collection&classifications=NFDI4CHEM it returns results both in prod1 and prod2. I will investigate why the variable names needs to change.