You are the first one reporting it for KFLL. We had a couple of users having this issue at KLAS, but nobody else reported it before for KFLL, perhaps it depends on the kind of AI models used and also their density.
We think it might be caused (and, apparently, it doesn't happen with all AI configurations) by the fact that FS9 doesn't have a native command, like in FSX, to turn off the default hold short zones drawing, in order to be replaced by custom ones, like we have at KFLL. Since it's obviously not possible to remove the hold short node entirely, otherwise the AI will just stop working, the only way to get rid of the default drawing, is to set the width of the taxiway at the hold short node to 1 ft.
In FSX, we don't have this issue, because there's a specific hold short node type that is not available on FS9, that works as a proper hold short, but doesn't draw anything, so it can be used safely for custom hold short markings, without using those tricks.
So, in either case we'll try to fix the issue, we would end up in one of those less than ideal situations:
1) keep the scenery as it is, and risk the AI bunching
2) restore the normal taxi width, and get double hold short markings, with the default ones that will bleed through the custom ones.
3) remove the custom hold short markings in the FS9 version of the scenery, making it even less attractive compared to the FSX one than already it is, because the default hold shorts markers really looks much worse and out of place, considering the whole ground markings are entirely custom.
A question: are you using the AFCAD that comes with the scenery, or the Harpsi's one ?