The window.
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29948572.cfm
Post of a fridge going through windowThey build campers from the inside out sometimes, so the interior and furnishings are installed before the outer walls sometimes. The window might be the only hole big enough.
If you have a big window that is an "emergency exit" window then you are fortunate as you can remove the window without removing the frame, often this is why there is an emergency window.
Good news is that you end up replacing the butyl around the window, which is something that is a maintenance issue after 10-15 years anyway.
Consider converting to the Danfoss type compressor fridge. Some propane models can be converted, or there are many chest type fridge/freezers out there. Dometic or ARB are two name brand ones, but many others on ebay that are similar.