[fitzroy]

This is definitely a known issue on 2012/14 the Mac Minis (USB 3.0). https://support.apple.com/en-us/HT203729

https://forums.macrumors.com/threads/usb-3-causing-interfere...

Apple's article mentions USB 3 devices, but the issue is very much with Mac Mini's ports. Moving the devices further away doesn't help much.

I have a pair of cheap Bluetooth earbuds. They have a range of about 30 feet with when paired with an iPhone and about 4 feet when paired with the Mini. Apple's Magic Mouse needs to be within about 4 feet to work as well.

[craftyguy]

The article here is from 2012, so not surprising that devices made as early as 2012 would be affected.