We're getting a "metafields.key must be unique within this namespace on this resource" error attempting to update metafields on a product via the REST API.
The key values are indeed unique; however, they share a common prefix that contains an "&" character. For example:
Is this perhaps causing the key text after the "&" (the unique part) to be ignored?
Are there special characters which should not appear in metafield keys? There is no mention of such restrictions that I have found yet in the Metafields API documentation...
Or are there perhaps key length limitations that are truncating the keys before the unique part is reached?
Test Urlencoding the ampersands for a change in situation.
We can certainly try sanitizations, but needing something like UrlEncode() on the key value should be documented...