Hi,
This might well be linked.
Searching for "setenv" in our code, the only place I can see it is in the MyParcel plugins.
It is used to change the server of the API for Belgium.
This follows the major update we did to the MyParcel plugin to update to the latest version of the SDK:
www.hikashop.com/forum/shipping-methods/...-updates/365244.html
The setenv call is only made for Belgium because for the Netherlands, the default API URL is already set to the Netherlands server.
So it smells like both the error in the backend and the issue on the checkout are related.
And your videos seem to go in that direction too.
Before the redirect loop happens, the payment methods area is updated, and the shipping methods area is empty, probably because it isn't able to load the area following the address being filled.
I think I didn't get the issue because I didn't use a real Belgium address, and so MyParcel skipped it, without triggering the error.
I've published a new version of the MyParcel plugins on our website with a patch for this error. Please download them and install them on your website and try again.