UTMs Truncated After First '&'. How to Resolve?

I'm creating shortened links via the API. UTMs after the first '&' are being stripped off in the response. I've tested using Postman, in the app I'm creating (NodeJS), and on the https://developers.rebrandly.com/reference#create-link-url "try it' feature.

Example URL:

https://something.org?utm_source=slack&utm_medium=social&utm_campaign=something&utm_context=anotherthing

What comes back (after shortened URL is clicked):

https://something.org?utm_source=slack

this gets stripped off ---> &utm_medium=social&utm_campaign=something&utm_context=anotherthing