what plasticity model are you using ?

bi linear or multi linear ?

are you loading by displacement or force ?

i have simulated necking with a 2D axisymmetric model with multi linear plasticity and displacement control, displace it to a reasonable level, you should be able to calculate what this is, for say 30% strain.

your high distortion elements warning is probably in the necking region.

Track reaction force and if necking has occured, you will see a peak force that then drops.