Hi @Joachim_Brindeau - sorry to hear you’re still having trouble with this!
I noticed you’re passing 101 values - perhaps one of these 101 items is using an an invalid value in any of the fields they are referencing in their Webflow node?
Can you try with one item at a time and see how that goes? For example, you could use a SplitInBatches node and run batches of 1, this should make it clear which item exactly causes the problem.
Webflow also seems to have some logic to their API that might be unexpected, take a look at this post as well to see if it might help. It might be worth checking with Webflow’s support team on what exactly is required of this request.