What am I doing wrong here? Changing civ emblems to tech tree ui

Context: I am maintaining my previous tech tree ui mod. It used to work well, at least mostly well. But today I met some weird problem that some of the civ emblems/tech tree will not show up.

My tech tree UI mod works similar to what Nixon has done, but I generate those civ emblems by some script that uses data from aoe2techtree.net. I am updating my mod since the new dlc comes out. But I realize Aztecs and Bengalis are not showing up.

I firstly found that both civ emblems are first two emblems to load in “materials.json”. After some experiments and debugging, I realize that it is the emblem pictures themselves not loading up, instead of other bugs. I test using a self-use mixture mod where there are other custom icon assests, too. If I delete the entire folder of “mymod\widgetui\textures\ingame\panels”, both civ emblems will show up. After I made some changes and cleaning in the folder, now Bengalis will show up. And during the cleaning, I found custom elements overlap my civ emblems.

Now I wonder what I have done wrong. Because if there is a limit of how many custom assets to load, I have definitely deleted enough number/size of them to make the space. Why does this Aztecs emblem still not showing up? Is there a bug here?