When a scripted find fails, there are two simple debugging tricks that might reveal a clue:
Temporarily remove the set error capture step so you can see the precise error message being returned.
Immediately after performing the script, select "modify last find" and inspect the find criteria used by the script to perform the find. You can even try modifying the criteria to see if you can figure out what change is needed.
I prefer to use a different approach to scripting a find as shown in these examples: Scripted Find Examples
But I'd try using a find criteria of just $ContactABID (no enclosing quotes, no = operator) and see if that works.
Also, the Perform Find script is overwriting any criteria you enter while the script is paused in Find Mode.