I wrote my own but you could try this... Flatten the UVs in their W coordinate before running the tools and see if that solves it. A number of UV operations cause shifts in W and that will mess with the maths used in the texel density tools if it's not accounted for.
Switch from UV to UW Inthe UV editor and scale the UVs down. It's probably a good idea to move them to w=0 as well Max stores UVs in 3d space, w is redundant unless you are using 3d textures. This won't necessarily fix it - I don't use textools- but it's the most obvious cause of UV fuckery outside of having genuinely bad…
Sorry I'm not sure how to flatten only on the W coordinate, how do I turn on that option? Flatten mapping only has polygon angle threshold and spacing.