API Request (Web Action) Relative Path Not Working

I have an API GET request working in Postman for testing:

[base url]/envelopes?count=750&from_date=2024-10-01&order_by=last_modified&include=recipients

When I set up a web request in Data Factory to do the same thing, I get an error message response:

{"errorCode":"INVALID_REQUEST_PARAMETER","message":"The request contained at least one invalid parameter. Invalid value for query string parameter 'from_date'"}

Looking at the activity inputs though there doesn't seem to be anything wrong:

{ "method": "GET", "headers": { "Authorization": "Bearer blahh" }, "httpRequestTimeout": "00:10:00", "relativeUrl": "envelopes?count=750&from_date=2024-10-01&order_by=last_modified&include=recipients" }

I've tried a few things like alternative date formatting and URL encoding but to no success. I can't really see what's going wrong here unless data factory is doing something to the relativeUrl after this. Any ideas? I believe this was working some time before christmas, I don't know if any changes to the platform have been made since.

EDIT:

Some further testing. I have another query which grabs user data which succeeds. However if I add in the relative path &additional_info=true, then the action fails. There must be some issue with handling this relative path.

EDIT2:

If I remove the relative path and include it in the full connection then it works as a work around. However this isn't acceptable as a solution as I need to be able to parametrise these optional items.