I made a short test flight with the dev console open and was unable to reproduce the issue, despite several DIR inputs. However I did see something weird in the console, maybe it helps, maybe not.
Cargo aircraft
EGPF/EGPH FL150 CI 11
WX : surface temp +01, pressure 29.50
Cargo 6167/6167/6167 fuel 50 000
Route : RW23 CLYD3A CLYDE DCT MAC DCT TRN DCT AGPED AGPED1E
Spawn on runway 23, EFB > load panel state Ready for takeoff
At 70NM from AGPED > Direct HAVEN
In the console, among other things:
SLOPE: 108.239
SLOPE: -nan
SLOPE: 101.896
SLOPE: 108.239
SLOPE: 98.9952
SLOPE: -nan
SLOPE: -0
SLOPE: -nan
SLOPE: -0
SLOPE: -nan
SLOPE: 263.438
SLOPE: -nan
SLOPE: 98.9952
SLOPE: -nan
Are those NaN supposed to be there?
I note that, earlier in the flight, immediately after the turn MAC > TRN I tried a Direct TRN , and all SLOPE messages in the console had a number (float).
Only after the second Direct did I see this weird stuff in the console.