There is a scanlines.png file that Mame includes with each release.
The file you are using is scanlines75x2.png which I could not find anywhere so either you made it yourself or its from a much earlier version of Mame.
Generally I just extract the latest release on top of the old. Eventually either something stops working or I house clean, starting over with a clean slate.
Anyhow, I love this feature. It would be cool if the tilt could be somehow tied to choosing full cabinet artwork. Or maybe a frontend could handle the setup. That would be the easiest method for now.
Please feel free to post your other tilt art layouts such as Tron. TiltART T_ART files. 🤣