I found an odd bug; if you disable "Digital Elevation Mesh" you can no longer designate targets with the SA-4.

Example:

1. Designate target with Long Track
2. Throw radar off dummy load
3. Activate automatic angle tracking
*Bug*
The guidance radar display doesn't show you're tracking a target, it remains in П (Pelengation) mode. If you attempt to change to the Target Designation Mode switch to Continuous, automatic angel tracking is canceled and the target is lost.

I found it, again a one liner bug...