Have you cleaned the bobbin area, the sensors are located there and might be fooled by some lint.

Welcome! Someone will be able to help you! You are going to love this site! I'll give you your third flower under you picture. Dawn

Is it not annoying when the machine thinks it knows better than you. Sometimes it helps just to rethread top and take bobbin out and reinsert.

It could be a little lint on one of the sensors, just clean it real good.****

WELCOME, YOU ARE IN THE RIGHT PLACE, HERE YOU WILL GET HELP FROM ALL THE CUTIES, THEY ARE ALL SO WONDERFUL, THIS IS HOME, THIS IS FAMILY. YOU GET LOTS OF HELP AND LOVE AT THE SAME TIME.

Hi and welcome to Cute. I would follow liqu's suggestion and possibly change the needle. Sometimes turning the machine off at the mains for 5 mins and starting again can help. Let us know what worked.

Could be that your tension has thread in it,,,or your tension spring may be broken.

I love my Brother and it does this sometimes but it does know more than I and when I completely unthread and re thread the bobbin and the upper, that usually fixes it for me.

WELCOME to this very addictive site! When my D1 kept doing this I took the bobbin out, removed the plate, bobbin holder and cleaned it well and used moisture free canned air and blew all the lint out. I was very surprised to see how much stuff was in there!
Good Luck ! *4U
Jo

My Brother machine did this the other day. When I took the bobbin out, reinserted, making sure it was unwinding in the direction that you slide the bobbin thread into the groove towards the needle plate, it worked fine.
Angel