Hmm, I restarted my computer and it suddenly worked again. (I think I might have tried restarting yesterday and it did not work but not sure).

Still would be good to have some ideas what could cause this. I dont want this happening on production :).

I came across this issue when starting to upgrade and modernise a L4.2 application.

Basically the way Guzzle 4 and >=5 work are slightly different.

https://gist.github.com/Caffe1neAdd1ct/7809a32a0a447947b0902873c24ab7f5

Hope this helps anyone still on L4