Grount Connect Proxy: 404

I had a working grunt setup for several months and without changing anything on my side the proxy stuff stopped working. It might be due to some npm update updates or system (os x) updates, but somehow my proxy broke:

I have the following proxy log when making a request:

/web/app_dev.php/oauth/v2/token -> http://gambify.sites.dev:80/web/app_dev.php/oauth/v2/token

And this results in 404 not found. However, if I coil my request directly to http://gambify.sites.dev:80/web/app_dev.php/oauth/v2/token everything works fine, so my endpoint is actually there. And grunt also implements request and proxies at that location, but I still get 404.

Has anyone experienced something similar?

Best wishes, Mark