UE4.26 - Foliage Instance shows asset materials in gray, why?

Hi, I used the foliage instancer tool to place a foliage mesh in my map, I actually did this process in UE4.25, now suddenly while working in UE4.26, materials load or not… after starting the project all those assets appear gray, like if they can’t or skipped compiling, then if I keep restarting my project, sometimes they do appear, sometimes they don’t.

But, If I place those assets manually… no problem, materials always work, no exception.

To test this problem, I applied those materials to the original meshes and also in the instancer to reduce to posibiity of failing, but… sometimes materials they just appear gray, which means that this must be a problem with the foliage instancer.

Please help!!!