They seem to not spawn anymore a certain distance away from the starting area.

At what distance do they stop spawning? What mods are you using?

Map:
https://imgur.com/a/cMlny54
Lets hope this works. You can see the start location in the bottom left. About half a map is full of machines. But beyond that nothing more.
I also explored a lot more in another direction but nothing more to the right or above this picture.

Modlist:
https://imgur.com/vP5fIAE
I doubt there is anything on here that interferes with map generation (i have updated the mod since taking this picture of course).

Again thank you so much for any and all time you give this.

Edit: Hm, just to try i started a new game and walked in one direction for 5 mins or so. They do seem to keep spawning in this new game.
I wonder, could that be because i started this game with mod version 0.9.1?

I looked at the map—it looks very strange. Try the latest version; I played around with the generation in version 1.0.0 and above.