Change Filament leaves a huge gob of filament on the purch tower and extruder is grinding.  

Impressive.  Is this the correct change-to filament?

If so your filament sensor is probably playing up.  Check the connections, check there are no whiskers or debris blocking the sensor, make sure it is responding correctly ... and let us know how you get on.

Cheerio,

RE: Change Filament leaves a huge gob of filament on the purch tower and extruder is grinding.

I would check the ir sensor tower- it can warp easily. Recently I started printing in an enclosure and the whole tower tilted (due to heat) and caused the ir sensor to not read the filament when it arrived at the extruder and the filament was driven into the extruder (grinding noise) and a blob came out the extruder. I just sanded the bottom of the tower with a piece of 220 grit sandpaper on a glass plate to flatten out the bottom of the tower and correct the straightness, remove the tilt, and calibrate the ir sensor.

Here you can see the slight tilt was enough for the jam to occur.

RE: Change Filament leaves a huge gob of filament on the purch tower and extruder is grinding.

I had the same issue during the first print. I had to check again the IR sensor. It was flickering when filament entered. After this no more issue with blob, excepted on purge line at the start of the print. Sometimes a huge blob occurs and extruder grinds. Not so common hopefully.