I do have time for this - something I know (as opposed to the CSS fonts).
Demo Project: loopScroll_JHSv1.hype.zip (149.7 KB)
The actual loop transition point is a little glitchy in this Demo - something that can be refined to your needs; but the principle is shown here:
• Tagging on a couple more elements, "Aa" & "Bb" (which are "A" & "B"copies), to the end of the group.
• When the timeline hits the spot where "Aa"~"Bb" are both in the rectangle mask jump back to the point in the timeline where "A"~"B" are in the rectangle mask in the same left position. So if "A"~"B" are both in the mask at 3 seconds and "Aa"~"Bb" are in the mask at 7 seconds, have a timeline action "Go to Time in Timeline" at 7 seconds that jumps back to the 3 second mark.
This will take some tweaking so the speed of the movement (frame to frame) will allow the same location in the rectangle mask for both "A"& "B". Adjusting the width of the mask might also play a role it getting it to work smoothly.
Also I just noticed the animation in the Demo has an "Ease In Out" timing. You would probably want to set this to "linear" instead. This adjustment will change the current synchrony of the animation. So make sure You select the timing function You want to begin with.