It was the same with Nexus 5x (LG made) and Nexus 6p (HTC made). Nexus 5x was a disaster.

While my 5x never suffered the dreaded bootloop, I will never buy another LG phone. In the time I used it, Google replaced it 3 times. And hang out on the 5x subreddit, it's filled with unhappy people.

Yes. I owned the Nexus 5x. Imho it was a horrible phone (especially compared to Nexus 5)

Nexus 6P was made by Huawei, which in my opinion accounts for its quality.

Was it the Nexus 6 which was made by HTC then?

No, that was a Motorola.

The Nexus 9 (tablet) was the only htc-made Nexus. And it was a piece of garbage. The first-gen pixel phones were both htc-made through, and seemed to be well made.