Hi Pete,
Sorry.
I'm setting altitude using VB.NET at this time using offset 0570, I have no logs, i did test with FSInterrogate, it does the same.
These are the values at startup with the aircraft on ground, and these do not change when in slew mode.
Buffer 1: 83626839613
Factored : 63.88088 - this is the correct elevation for YHBA
It only does it if the aircraft was sitting on the ground when using slew mode, I entered slew mode via keyboard not code. The only thing I can see is that the aircraft sinks a little
To duplicate;
Start FSX, enter slew mode, you'll visibly see the aircraft sink a little, try and change altitude, nothing happens, move aircraft via FSX using slew a little of the ground, and all works fine.
Cheers,
Charlie