Checkpoints position preventing boss spawn/respawn?

As I play the game it seems to me some checkpoints are messing up the spawn of bosses/content. Maybe because they were placed too close... I don't know

Why I believe this is the case:
- Some bosses respawn when I die; some do not, and it seems to that the checkpoint in the ones that don't are quite "too close"
- I find some checkpoints in some "random places" that really look like should have a (boss) fight. Still, they are empy (just like the area of bosses that did not respawn, like I mentioned before).

One such example:
- https://imgur.com/a/A0p4qPj
- location: Bone Pit (act 2 cruel)
- location was empty when I found the checkpoint and the area.

I suggest taking a look at the added checkpoints and if indeed they are affecting spawns, see about moving them away a bit.