Admin display and functionality not working properly

I’m filing this question under miscellaneous, because because I couldn’t find the ‘bizarro’ section.

So… I’ve got a wordpress site that I built for testing on a shared hosting package (GoDaddy)… all looked OK, close enough to finished I set up GoDaddy Managed WordPress Hosting and migrated the site there to finish off get it ready to go live.

This is where it starts to get bizarre…

I’m getting numerous problems trying to do anything with the site on it’s new hosting home. That is… I’m getting these errors and problems only when trying to work on the site from two specific machines. (Unfortunately, my two primary work machines).

Both these computers are Win 10 machines. One desktop and one laptop.

I have no trouble when accessing the dashboard from from old Win 9.1 machine, or from a Mac or (having checked with a friend)… other Win 10 machines.

I also have no trouble with any machine… working with the test site that is still sat on my shared hosting package.

So, logically… it’s not:

An installation problem (it works on other machines)
A hosting problem (it works on other machines)
A faulty site migration (it works on other machines)
A theme/plugin problem (it works on other machines, AND… I deactivated everything and switched to the default 2016 theme, and the problem still persisted… on the two machines I’m having problems with)
A browser problem… the problem persists on 5 different browsers on those two machines and I’ve cleared cache several times and rebooted several times.

So… it’s a machine problem, right?

Well… apart from the fact I have no trouble on those machines, working with the exact same install, with same plugins, etc… on the test site on my shared hosting package.

So… what the hell can be causing the problem?

Checking the browser dev console for errors, changes depending on which browser I’m looking on the the time, but the following is typical:

Consider using 'dppx' units, as in CSS 'dpi' means dots-per-CSS-inch, not dots-per-physical-inch, so does not correspond to the actual 'dpi' of a screen. In media query expression: print, (-webkit-min-device-pixel-ratio: 1.25), (min-resolution: 120dpi)

.../wp-admin/load-scripts.php?c=1&load%5B%5D=hoverIn…-audiovideo,mce-view,imgareaselect,image-edit,wpli&load%5B%5D=nk&ver=4.4.2 Failed to load resource: net::ERR_CONNECTION_RESET       script.js?ver=4.4.2:2

Uncaught TypeError: undefined is not a function

So… load-scripts.php shows up in errors often, so does a date picker error and a color picker error… all seem to be script errors, but… if load-scripts.php was corrupted in some way… surely everyone, from whatever computer or OS would be seeing he same problem?

Oh and… yes, I’ve talked to GoDaddy support. Spent about 90 mins across two phone calls with them, and… they’re simply not seeing what I’m seeing, and therefore have no useful suggestions.

Anyway… the site is impossible to work on with either of my main work machines. Page builder doesn’t load, YOAST SEO only loads some sections, media uploader comes and goes and various other section only partially display, or simply don’t function… such as getting “Error code 101 (net::ERR_CONNECTION_RESET)” when I try to save a setting or something.

I’m literally at my wits end with this.

If anyone has even the faintest idea of what might be going on here, I’d sincerely appreciate any and all help I can get.

Thanks. ??