I know theres another thread on this but I thought this fix might be useful for a sticky:
The main prob here is the assembler quality - links placed on it are loose and prone to jumping out. After doing 75% (and getting RSI) I found an easy way - I searched the forums but found no similar method)
Place the assembler on a piece of double sided tape (I am right handed so the link holes will be on the right. At the top and bottom stick more DST and strip the protection.
Now place the links (1 and 3) to be joined on the assembler (2), and working from the assembler outwards, gently press the track into the tape.
Track now does not rock or jump, and wire/rod almost glides in