Multiple Filters in Document Library - Not Working

[Aravind Sukumaran]

Current Library/Site Setup:

• I have a document library XYZ with columns a,b,c,d.
• 'a' and 'b' are lookup columns (from a different list in the site)

Issue:

When I filter with 'a' or 'b' separately, I can see the documents without issue. 
If I filter with 'a' and 'b', it gets filtered but no documents are listed. 

Same time, if I filter with 'a' and 'c', it is working fine. 

What could be the possible error? Is this something to do with the column?

[#2]

@Aravind Sukumaran 

Are you maybe using the modern experiance and seeing a "folder" when you use a few filters in combination?

I now have two clients that cannot use Metadata filters to properly filter their data as required.