The new TeX file is only created, if missed or older than the related png file.
=> Touch it the new png, so that it is younger than the file without ".png".
Or remove the files without ".png", so that they must be re-created from png.
Then repeat step 4
You can verify it b looking at the file dates.
EDIT:
There is a third way: Option --encode-all
=> wszst create strap.szs.d -od new-strap.szs --encode-all