DRV8825 + REPRAPGURU NEMA 17 42STH40-1204 Low voltage? Low current?

Projects General Guidance
5

Measure the resistance of the two coils. If there is a significant difference then one of them may be faulty.

When you said "KS42STH40-1204" did you mean "KS42STH40-1204A". I didn't find many references to "-1204" but plenty for "-1204A"