Failed to merge bones, even though it should work

Hello!

I’m new to UE4, and I tried importing several models as fbx, and as a Skeletal Mesh of the first one (I need to import few animations for each model later).

So I have 4 models, 3 animations each. I import first one (let’s call it A), everything is fine, animations are working, I’m moving onto importing another model - I choose the first one (A) as Skeletal Mesh while importing second one (B), it goes pretty well, animations are working as well, same for the third (C) model, everything works, and then, the problem occurs. Whenever I’m trying to import fourth (D) model with the same Skeletal Mesh choosen as before (the first one (A)), it gives me an error that it failed to merge bones. Huh, I would understand that if the file would be different than others, but then, even more strange thing happens now.

I removed everything again, and imported other model as the first one - the B one. Then I imported second model, I choosed the B model as Skeletal Mesh in import settings, and everything works again. Now! Im importing the last model that wasn’t working last time, choosed B as a Skeletal Mesh while importing - and wow, now it works! But what with the other model, that was working before? I try to import it, and now this model gives me an error that it failed to merge bones.

Concolusion/tl;dr - 4th model which I try to import as a skeletal mesh of the same model as everything before (1st/2nd/3rd model) won’t work, and no matter which model is it - simply just gives me failed to merge bones error.

Anyone experienced such problem before? Maybe I’m the one who’s making a mistake?