Start by changing your setter:
if (Math.Abs(_Qty_To_Move - value) >= 0.001) // Some threshold value suitable for your scenario
_Qty_To_Move = value;
If that doesn't resolve it on its own (you should do that anyway), you might want to try specifying a string format or using a value converter. I think changing the setter should be enough.
Hi Jessie, I changed it to Entry and got the same issue. Are you updating the interface in the set of your property. Below is my code for the property.