French to English Tech/Engineering Manufacturing light and sound-based warning systems for vehicles

I'm really hoping someone is going to tell me that I'm segmenting this sentence wrongly, but I have looked at this for so long now I can't see the wood for the trees!

It's from the Guarantee clause of a contract for the supply of light and sound warning equipment for emergency vehicles.

..."[name of company] se réserve le droit de facturer à [name of supplier], après consultation et accord entre les deux parties:

- les frais de stockage afférent aux Produits refusés,
- les frais de transport occasionnés à l'occasion de la mise en jeu de la garantie,
- une participation aux frais de retouche ou de tri en cas de rebut à la reprise de retouche ou d'obligation de tri au-dessous un certain pourcentage,
..."

I am currently working along the lines of "a contribution to the modification and recycling costs if rejected products require further modification or the volume of products recycled exceeds a certain percentage."

I am unsure whether I have correctly segmented this sentence, and also am confused as to how the company can invoice the supplier for modification work, or indeed "further" modification work. Surely the supplier would have carried out any modification work?

I feel I'm missing something with "reprise de retouche", particularly being prefaced by "rebut".

Any ideas very gratefully received, as deadline is fast approaching!