Contacts are missing

Contacts on the Apple Watch are handled by the Watch app on the iPhone and how you have it configured. Make sure you have it set to Mirror my iPhone. If that is done, then you can reset the Watch. Press and hold the Digital Crown and power button together until you see the Apple Logo and then release. The Watch will reboot.

Somehow that sync is broken. Try making some small change to one of those contacts in the A-D range. Will that change appear on the watch too then?

You could try the Reset Sync Data option to fix the issue, as described in here:

https://www.lifewire.com/resync-apple-watch-5186567