SkyRC MC3000 charging issue

I have a MC3000 charger which suddenly developed a strange problem in which is refuses to charge a cell in the 4th slot. It measures the voltage correctly but when you start charging a 18650 at 1A the current displays as 3.5A but when measuring the charing current it stays at 0A. All other slots work correctly.
I tested this with multiple 18650's and also with a couple of Eneloop batteries to test the NiMH functionality.

Has anyone seen this issue? My charger is still under warranty but if it is a known issue with a known fix I can try it myself.