Universal FMC, some navaids won't insert

Hi,

I have loaded a flight plan using the P3Dv4 flight planner, and can see the plan in the Universal FMC. If I try to add extra waypoints enroute, sometimes it works ok, sometimes it doesn't. These exist in P3Dv4 as I can add them through the default flight planner without issue.

An example is the RWY NDB at EGNS. If I enter RWY and press enter nothing gets added and the plan is unchanged.

I have also had this happen with various intersections.

Any help would be appreciated.

Regards

Phil