nGen filament end of roll distortion

I just had a failure of a print due to stripping of the filament.
This is the 2nd time I’ve had this and it’s because of filament distortion.
I was getting near the end of a roll of nGen and I had a print fail due to stripping.
I thought the spool had hung up, but now I’m not so sure.
I changed over to ABS material, fresh spool and things were going well.
Then, I went back to the nGen material.
There was only about 64 grams of nGen left and my project only called for about 40 grams.
Things started out good, everything going good until the project was about 75% complete.
Then the filament stripped and would not feed.
I knew that the filament had not hung up anyplace and upon looking closely, the filament looked like an oval instead of being round.
I measured it as being 2.35mm in the winding direction and 3.2mm in the other direction.
It appears that 3.2mm is too large for the TAZ6 extruder.

Question now is:
Is it typical to throw away the last 100 or 200 grams of material at the end of a roll of filament?

Does anyone know of a filament alarm that would alert the machine operator if the filament is no longer round?

Thanks in advance for any words of wisdom on this subject.

There isn’t any extruder that can handle an oval shape filament. 3.2mm is too much to handle. Even 3.1mm can be a problem. This is the reason most filament manufacturers choose the 2.85mm dimension to give them some space for error!
I’m quite surprised for your experience since nGen is supposed to be good quality filament. And you shouldn’t have to throw away any piece of filament. You should be able to use it all the way to the very last millimeter. Probably something went wrong with the batch you have. In any case if I were you, I would let ColorFabb know about this, no doubt.
As for your last question about a device metering real-time the roundness, I’m not aware of anything out there.

That is unusual. I run a lot of nGen and have used every roll down to the last few millimeters and I haven’t experienced any problems. Maybe it was a bad batch. I’d definitely notify either the vendor you got it from or Colorfabb directly and see if they can help you out. They will probably want a sample of the bad filament and the info on the side of the box it came in.

I sent a message to the Lulzbot support people letting them know what happened.
I’m not looking to get anything out of this, I learned something about filament with this experience.
I’m quite new to 3D printing and I really like my TAZ6 printer.
By The Way.
On the ColorFabb nGen spool, it says manufacturing date April 21 2016.

My new spool of nGen was manufactured in August of 2016 and it’s working good.
I’ll be watching this spool when it gets close to empty.

Thanks to all who commented for their words of wisdom.