The needle is out of sinc with the bobbin carrier and striking the casing of the carrier. How do I resolve this

SOURCE: Needle & Bobbin out of sync

This description sounds like the machine is out of time. The needle should match up with a cut out section in the bottom of the bobbin area. If it is hitting, the timing has slipped, probably from sewing on a fabric that was too heavy for the machine.

SOURCE: bobbin case retainer popping out on Singer Touch & Sew 625

Take the bobbin case out. Then when you go to put it in, realize there are 2 ways to get it. You have found one way. The other way is first look in the the slot with a flashlight before you insert it. There is a flat piece of metal the bracket needs to be slid under as it is inserted. This acts like a spring making it tight

SOURCE: needle hitting bobbin case model 750

This is a timing problem the hook timing needs adjustment, and possible the needle timing also

SOURCE: needle hits bobbin case...

If the needle hits the bobbin case the are only 2 things that could be wrong. Lets hope its the easy one, there are more than one length of needles, if the needle is to long or it is not all the way up in the neelde bar, the needle will hit the inside of the bobbin case. Now if that is not the problem then the machine is out of time. ALWAYS check the easy stuff FIRST.

SOURCE: Needle breaking, hitting bobbin case

I had this problem and it is very easy to fix!
With mine I looked at it for about half an hour, and all I needed to do was put the bobbin case back in,(how it fits normally) and then hold it and turn it anti clockwise until it clicks, it may be quite pressured to do but ive heard a lot of people having this problem and thats all that needed doing!
Hope i helped! :)