If the flickering is fast, then it is more likely to be a wiring connection or ground connection. The regulator can produce this type of thing, but it won't be fast, as the battery is in the circuit and its voltage won't change that fast. A faulty connection, either in the supply or ground wiring, can change resistance fast, to produce this type of fault.
Digital meters can read fast changes, depending on the refresh rate. Cheap ones are slow. The better ones can read, and record, instant maximum/minimum voltage changes.
I don't think it is the regulator.
Harvey.
