That sounds to me as if the size like 1300px was just to large and probably upscaling the image causing your server not being able to handle this. This is any case something that needs to be figured out individually as all server are different.

I cannot help with the Colections themes. You probably have to modify it. Perhaps try to contact its author, perhaps via its GitHub repo: https://github.com/RolandTi/collections/issues

IE is really not a browser anyone should and does still pay atention to. You wil have issue with that everywhere by now. It is totally outdated and Edge the successor already (which I don't know being a Mac user)