Now why is it whenever an issue is pointed out - people always assume it's because you - specifically have that issue ?

I've been in IT since it was invented. I'm not saying that networking has not improved. Just that it's never going to be as reliable as reading from storage directly connected to a device.

The longer the distance tha data has to travel, the more opportunities are introduced for 'issues'. That's just common sense.
Uploading the entire file directly to a usb connected pi, is a good option. Incrementally adding it to the same pi during the course of the print - over any network - isn't as good an option.

What cell phone do you have ?
:-)