I once accidentally transposed two digits of the ramp Lat and Long during my flight prep, without realising, and PM did not spot my mistake as I did so, (SOP was for us both to check the figures as PF put them in), and we took off, only to receive a Navigation position uncertain caution, (A321).
This resulted in us stopping climb and reverting to navigating direct to a VOR, old school raw data, and landing back at the original airport, for the engineers to check the aircraft.
Red faces all round and a 2 hour delay, but we still had to fly the whole duty, 4.5 hours each way.
So perhaps the new SOP is a good idea?