[PaulHoule]

Variable-length instructions cause one bit of inconvenience for assembly programmers.

There are long and short JMP instructions that your assembler can possibly choose between depending on how far away the target is. Now, changing a JMP from short to long can change the length between another JMP and the target. Assemblers have different levels of intelligence for this situation: I programmed a lot of assembly for the 80286 (not protected mode but I used all the instructions that would speed up real mode) in the late 1980s and since we were working with little space a good assembler would try assembling the program multiple times until it got a consistent solution for what kind of JMP to use where.