Yes I would definitely change the needle, I would also clean and oil the machine.

Loops can drive one crazy. On my older machine, it meant that I needed to take it in for servicing.

Try a different thread in the bottom keeping top the same after cleaning and changing needle. If this doesn't work try different thread in top the one you want to use in base. If still not working try different thread top and bottom.
a few weeks ago I sorted a friend's singer. I did each step separately as so many things were wrong, plus a needle had been inserted (forced) into the wrong place. Finally after an hour got it going beautifully.

90/14 topstitch needle. Make sure your thread is in the take up lever. NEVER MESS WITH TENSION IF FMQ...until you sew feed dogs up, normal straight line of stitching...if your tension is ok, then it is probably ok with FMQ.50 WEIGHT THREAD...40 is ok too. Let us know if it was the needle.

Make sure your bobbin case is seated firmly in the machine. I had that problem on a Powerquilter 16.

This happened to me before, take everything off thread, bobbin and your machine plate off and clean your bobbin area out with your brush. Replace new needle, and re-thread, and see how things work. Make a sample sandwich quilt if you changed your stitch length start back at default stitch and try again then if the stitches are not what you want then adjust once you have the look you want write down the adjusted stitch and width. Hope this helps

This video from Man Sewing might help you with your thread problems. https://www.youtube.com/watch?v=thQ7bSTqMFU

I have plastic bobbins for one of my machines. When my stitching creates loops, either top or bottom, I have been able to correct it by using a new plastic bobbin. I have been told by the Brother repairman that the plastic bobbins warp. Also, make sure you are using the correct product number for your bobbin, the one your manual specifies. It does make a difference for success. Please be sure to publish your "fix".