Yeah, it looks like that is the problem. I can still replicated it when I am logged in, by clicking on Modules, search for "plaits", and scroll down to the bottom and click the Mutable Instruments Plaits module. Same problem when I am not logged in, and in another browser.
Using the direct link https://modulargrid.net/e/mutable-instruments-plaits also does not work, except when I use a browser I never used before.
When removing all cookies it works.
Logging in again, and search for plaits - exactly the same problem.