You are not charged when the DEM processing fails and you get no result.
The rest of your jobs are not really failing but they are not turning out well because the DEM you are providing has a roughly 25 meter GSD and is only a few pixels in size.
Unless this area has been heavily modified you are probably just best off using the SRTM data if you only need that big resolution.
If you need to use the custom data please upload larger areas and try to use a source that has smaller GSD.