# JavaScript (ES6), 26 bytes

_-1 thanks to @thejonymyster_

_-7 thanks to @Arnauld_

_-4 thanks to @l4m2_

    x=>x.replace(/-2|1/,z=>~z)

Swaps the first instance of `-2` and `1`, saving 1 byte when the program compresses itself. Takes the list of bytes as input, as a string.

This is quite the community effort now :p