I have a Core which works but seems to struggle to connect to the battery section of the unit. Originally I thought the battery was just old but I bought an additional battery module and it still wouldn't run unless I connected it to power via the usb c lead.
I checked the voltages on the pins from the back of the battery pack (whilst mated with the core and plugged in) and it seems that the Mbus connector is not actually connecting (5v not present) so I wonder if the terminals female socket on the main board are worn out. I tried off setting the pins slightly and it helped a bit but not enough to make the connection reliable when fitted together.
Does anyone have any suggestions? I could try and replace the Mbus socket but it's probably more trouble than it's worth. I might just have to stick with it being tethered but now I have a spare battery module I can't use!