I see you are using a hostname for your groov box. How was name resolution handled in this scenario?
This really smells like a network issue to me - short DHCP expiration; flaky DNS name resolution; duplicated IP addresses; bad equipment and/or wiring; messed up IPv6 configuration. That’s where I would focus. Maybe start by seeing if the issue happens when you connect using the IP address instead of hostname.
That’s what it looks like from here too. That said, it’s possibly an issue that the browser is requesting those images at all: they should have already been cached. I need to go double check the caching headers.
EDIT: Caching looks fine here, nevermind.
The fix ended up being just calling event.preventDefault() during the mousedown handler to let the browser know that we’re handling it. It was a weird interaction: it wasn’t that the button (an SVG element, not a button element) was being dragged, it’s that it allowed you to drag and select a bunch of other stuff, and that whole bunch of other stuff was draggable, which could then confuse the event handling.
Quick one line fix, thankfully. 
Awesome, I love those.
The hostname was just a means of differentiating units in the shop, we only access them through IP. But yeah thats where my attention is focused this week. Thanks for the leads, Im going to start poking around.
Yes, thank you very much for your help with this. That has eased tensions here tremendously. Im glad it was a simple fix.
No problem. Looks like it’s been there since we introduced that button, it’s just way more likely to be triggered on a PC touchscreen than with just a mouse.