modx->sendRedirect not working after provider migration - modx version 2.8.5

Summary

I’ve been migration our modx package to a new provider. After changing all paths (hopefully) the site seems to work just fine again.
The only problem is the Snippet FirstChildRedirect which causes a blank page.

I could trace the error to the modx->sendRedirect which seems not to work. The url it takes as argument looks ok and is not different to our old environment.

Any ideas?

My current workaround is a javascript window.location.replace command but this just a bad workaround for sure.

Any help appreciated

Thomas