Did you check the bobbin tension? You should be able to check it just like on the Kenmore.

My vertical bobbin Pfaffs and now the Brother 1500 have guides to check.

The one time I had the same problem with my Bernina I had the bobbin unwinding from the wrong side and the thread was slipping out of the bobbin case slot. It would sew but sew awful. Check to see which way the bobbin thread is unwinding off the bobbin. Too bad you gave away your Kenmore. :(

I am assuming you are aware Bernina bobbins are specific to machines. You can't slap any old bobbin in the machine. And even different Bernina models take different Bernina bobbins. Also Bernina's need to have the thread feed a specific way. Once you put the bobbin in the bobbin case pull the thread and ensure that the bobbin is rotating clockwise. Have you noticed if your machine is having problems with only one specific bobbin? It could be warped or otherwise damaged but not that you would visually notice. That could also be the problem.

Finally, I do occasionally have this problem when I am running Superior bottom line in my bobbin. I need to tighten the tension on the bobbin case just a wee bit.

YES YES YES, get a Brother. Mine is four years old and has NEVER had to go to the shop.

This may be a bobbin issue that will require a new bobbin case? Take it to a dealer and have it checked. Worth everypenny. I LOVE LOVE LOVE MY 2 Berninas. (Also had trouble with the bobbin in my 200).

I don't know where you live or whether you are near a Bernina dealer but I would be on their doorstep in a hurry if I possibly could. That would make me positively totally frustrated.
I work on an Elna and a Janome. It always helps to have a spare.

I had a top of the line Kenmore before I bought a Bernina Artista 180. I loved that Bernina! When I traded it in for the Artista 200, I wanted that 180 back. I never had a problem with the 180. Others have given you excellent suggestions, e.g., re threading, being sure you have the correct bobbin, etc. If none of those work and a Bernina deLer is near, take it in and have it serviced. I gave my Kenmore to my granddaughter. When I have to sew on it at her house, I wonder why I ever liked that machine. I'm a real Bernina fan and I think the 180 is a great machine.

A mess on the bottom is not a bobbin issue, it's a top thread issue. There are any number of things that could be causing it. Check the manual carefully and make sure the top thread is threaded correctly. Make sure nothing is impeding the thread path as you sew. Try adjusting the top tension tighter. Make sure your thread size is matched to your needle size, maybe try a larger needle. And this one is sort of obvious, but we've all done it - make sure the presser foot is down.

As others have said, maybe it simply needs to go in for service. A good service tech will take time to show you things and answer all your questions.

I agree that I would take it to a dealer and have them help you figure it out!! I have two Bernina's and have had to have help figuring out tension on both! I now know more tricks to try!!

That is exactly what it was, a top thread issue. I took the machine and sample to the Bernina dealership and that is exactly what she said. It was either because (1) I didn't thread the upper properly (2) the feed dogs/foot was up when I did it, I didn't know that part so it was totally operator error which I am thankful for

I did leave the machine to have it serviced any way so I do feel better. Thank you everyone for listing to me rant.