How big (in kb or mb) are the .jpgs? If you convert them to .png, you could use a site like tinypng.com to make them much smaller.
Tried that too … reduced quality to some extent too. Same issue. Currently size is 900 kb approx
I would suggest using a single global Runtime listener to move all background images with a for loop.
There’s no need for each image having it’s own runtime. Maybe the gap (assuming the initial positioning is correct) is related to this too?