facets appear "_empty_"
Facets, by their very nature, work best when you use them for 'select' type fields, not pure text.  Facets work very well - and automatically - with taxonomy terms for example, because terms are re-used and it's easy to group based on select type fields.

Whenever I've wanted to use custom fields as facets, I've implemented them as terms (tagging) or select fields, and then they work properly.

So, I'm wondering - is that something you could do?  Rather than setting up your fields as 'text', could you set them up as select-type fields (whether it's tags, which don't have to be predetermined or select options which you have to enter in advance)?  That type of field is easier to GROUP by - which is what facets are really doing.

It may not be an option, but I have a feeling that would resolve your issue.

Let us know how this gets resolved!