Menu manager - weird text after adding item

[jelle-burodeng]

In the menu manager i select a link to an addon (eq structure). After clicking save i'm getting "{"selectList":"\t
\n\t\t
\n\t\t\t
\n\t\t\t\t\n\t\t\t\t\tLoading</span>\n\t\t\t\t</label>\n\t\t\t</div>\n\t\t</div>\n\t</div>\n"}
The menu item is set anyway, just the response is borked

"In EE 7.2.12 on php 7.4

[intoeetive]

@jelle-burodeng does that happen with any link that you add, or just Structure? Does that also happen on other pages?

I wasn't able to replicate that so far

[jelle-burodeng]

it happened with both a structure and a freeform link

[intoeetive]

If you open browser dev console with Network tab - do you see anything in red, any error? If yes, what the error is?

(I've not been able to replicate it so far)

[intoeetive]

@jelle-burodeng are you still having this issue?

If yes, can you inspect the browser dev console for:
a) any errors
b) the content-type header for the create-item request. It should be similar to this Content-Type: application/json; charset=UTF-8 and I wonder if it gets sent with text/plain or other content-type instead