your first screenshot indicates that the file is too large for SNAP to produce a quick overview. But as shown in the second, the data is not correct as well.
Please go through all input files (_split_Orb) and visually check if all contain correct data.
As for the stacking, I recommend to only use VV because VH doesn’t bring you any benefit regarding phase information (I made an example here: Effect of polarization on interferometric products). Furthermore, it reduces the file size of your stack by 50% and for InSAR you can use only one polarization anyways.
Finally, you can create an RGB composite after back geocoding using intensities of different dates to see if all were included correctly.