Here's my best guess:
When you're filling the data into those fields, you're using the "SetText" method on the component to set the text value rather than "Keys". Sometimes, in applications, there's an "OnExit" event that fires upon exiting the field that triggers other code. MOST of the time, the SetText method works fine with this but there are few occasions where this kind of problem happens.
Try changing to use "Keys" instead of "SetText". If that still doesn't work, add a "[Tab]" character at the end of the Keys string to tab to the next field to trigger that OnExit event.
