DIAGNOSIS This is physical wear from repeated plugging and unplugging, or from putting sideways pressure on the cable while it's plugged in. The port's internal solder joints or the housing itself is failing.
FIX Be very gentle. Use a high-quality USB-C cable with a snug but not forced fit. When plugging in, make sure the cable is perfectly straight relative to the port. Consider leaving a dedicated cable plugged into the wall adapter and just connecting the blender to it, rather than constantly re-plugging at the blender end.
IF THAT DIDN'T WORK Try cleaning the port. With the blender off, use a dry toothpick to very, very carefully scrape around the inside center tongue to remove any pocket lint or debris. Do not bend the tongue.
HEADS UP If the port becomes completely unusable, the unit is effectively dead. There's no wireless charging or alternative power input. Handle this as a critical point of failure.