PUT /customers/XYZ.json getting incorrect 422 "customer_tags" "is invalid" response

This seems like a bug on Shopify which we can reproduce reliably.

Current tags: "Affiliate, Affiliate Group: Nutriólogas" <-- note non-ASCII character

New tags provided in PUT request: "Affiliate,Affiliate Group: Nutriologas"

Response code: 422

Response body: {"errors":{"customer_tags":["is invalid"]}}

Response x-request-id: ad875558-f73a-4550-b9fd-15d9ec4f2d8a

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On my end I verified that tags don't contain any weird unicode characters - they don't.

I did not attempt any variations of this request because I don't want to complicate debugging. Let me know if you need information other than x-request-id.

Founder and tech lead for Simple Affiliate:
https://apps.shopify.com/simple-affiliate