I believe in Mojave the Accessibility “Reduce transparency” option is less effective (ie, it “reduces” less), which may make image matching more difficult and require more fuzz.
I tried increasing fuzz a bit, but then it found a different ‘line’ ;-( but I am fine with this solution. The inclination was to find the basis for an image ‘close to’ but this experience has taught me that its best to find one undisturbed image source, even at a distance, so I have learnt a bit more.
AND I experience daily enjoyment over the ease these macros bring into my workflow 
Kind regards
Palle Jensen