Modified NEC program is not particularly user friendly. I have devised it for my own use.
Error messages are sometimes misleading.
The optimisation is done for 144.0 and 144.5 MHz simultaneously. Of course the accuracy is influenced but the result is accurate enough to allow a judgement. Stacking distances 3.37 x 4.05 meters. The first observation is that the impedance is not very close to 50 ohms. This means that moving elements for a better impedance match will cause a less good optimum, the structure is not flexible enough to allow correct impedanc simultaneously with optimum for the other desired properties.