Very strange.
Lets confirm a few things
Firstly, is runwayhd taking its position information from PAW or the internal iPAD GPS ?
(Just checked, and this is configurable in runwayhd)
When stationary, were the two in agreement, or offset ?
I am trying to ascertain if there is a constant offset of 5nm, or whether there is a latency.
If there is latency, then after you completed your journey there should have benn a catching up of the positions
Thx
Lee