Lenovo has long had a separate board for the power connector you could separately replace. This is likely a continuation of that idea. I had an X220 Tablet (Released in 2011) from eBay that was sparking when I plugged it in. IIRC I just unscrewed and rescrewed the charging board and then it worked again. I guess there was some short, maybe it was loose. It would've been easy to replace just that part if it had failed completely.