Yes I think the culprit in all this is Illustrator which is continually being ‘updated’. I tried a couple of other svg graphics and a common problem is that often I need to rasterise at 300 to get a reasonable image. Illustrator then warns that it’s big and tracing may be slow. I then find that I am unable to get a trace preview even after increasing the stroke to 100px (maximum). The preview is an incomplete image.
I am finding it quicker to export as transparent png and then manually draw a stroked path on new layer (s) and save that to svg. It’s quite quick with a tablet.
Thanks for posting your results!