Grimm's law and verner's law

2.6. Verner's law in Gothic
Whereas the North Germanic and West Germanic languages clearly show the effects of Verner's law, those patterns seldom appear in Gothic, the representative of East Germanic. This is usually thought to be because Gothic eliminated most Verner's law variants through analogy with the unaffected consonants.
Significance
Karl Verner published his discovery in the article "Eine Ausnahme der ersten Lautverschiebung" (an exception to the first sound shift) in Kuhn's Journal of Comparative Linguistic Research in 1877, but he had already presented his theory on 1 May 1875 in a comprehensive personal letter to his friend and mentor, Vilhelm Thomsen.
A letter shows that Eduard Sievers had hit on the same explanation by 1874, but did not publish it.
Verner's theory was received with great enthusiasm by the young generation of comparative philologists, the so-called Junggrammatiker, because it was an important argument in favour of the Neogrammarian dogma that the sound laws were without exceptions ("die Ausnahmslosigkeit der Lautgesetze").
Dating the change described by Verner's law
The change in pronunciation described by Verner's Law must have occurred before the shift of stress to the first syllable: the voicing of the new consonant in Proto-Germanic is conditioned by which syllable is stressed in Proto-Indo-European, yet this syllabic stress has disappeared in Proto-Germanic, so the change in the consonant must have occurred at a time when the syllabic stress in earlier Proto-Germanic still conformed to the Indo-European pattern. However, the syllabic stress shift erased the conditioning environment, and made the variation between voiceless fricatives and their voiced alternants look mysteriously haphazard.
Which applied first: Grimm's law or Verner's law?
Until recently it was assumed that Verner's law was productive after Grimm's Law, and this remains the standard account: R. D. Fulk's 2018 Comparative Grammar of the Early Germanic Languages, for example, finds that 'Grimm's law should be assumed to antecede Verner's law'.
But it has been pointed out that, even if the sequence is reversed, the result can be just the same given certain conditions, and the thesis that Verner's Law might have been valid before Grimm's Law—maybe long before it—has been finding more and more acceptance. Accordingly, this order now would have to be assumed: