Does a firmware update make it better, worse, or unchanged?

I’d be checking them out of the box and seeing if newer firmware fixes it or breaks it.

I don’t know those televisions, but it’s not unheard of for Sony to outsource core products. Back in the day we repaired dozens and dozens of Sony VCR‘s that they made, and then they came out with a less expensive line that was made by Funai, different animal.

i know 10-15 years ago they had some cheaper models that did not have discrete power.  Only saw a couple, fortunately.

Outsourced, maybe that is what you are seeing.