@pip ...well done pip! It is a bit daunting isn't it but just think what a dab hand you are now at problem solving with it!
I nearly damaged my first overlocker within a few weeks of having it because I didn't read the instruction book properly: I ran it without any oil
(manual said to "oil before first use"), and I also tried like a titan to pull the threads out backwards
the way you do when you finish sewing on your sewing machine and couldn't understand why the threads wouldn't release!...that poor overlocker!