This is caused by inconsistent settings between SubVI Node Setup and Customize Windows Appearance in VI Properties.
To prevent this from occurring, you will need to do the following:
- In the VI that calls the subVI, right-click on the subVI whose front panel you want to appear and select SubVI Node Setup... and then select Show front panel when called.
- Open the subVI and go to File»VI Properties»Window Appearance»Customize and select Show front panel when called.
If you do not want the front panel of the subVI to show, then follow the steps outlined above, but be sure to uncheck the Show front panel when called
in both instances.