Key brackets problem

[Truthkey]

Hi there! I'm not sure if this topic should be in this section so if it needs to be on a different section, please move it for me. Thanks.

Anyways, on topic, I'm having a small problem. I have some rigged models that when I import them, they display bounding boxes for each bone while other models I have don't do such a thing. Here a picture demonstrating what I mean:

I don't have that many problem in 3ds max itself because I can disable them by going to "Customize>Preferences>Animation>Key Brackets Display:None", but when I export the models to other autodesk programs such as motionbuilder, they cause problems like this one:

Mainly, bones not appearing in the right way. So I'd like to know what causes those boxes to appear and if there is any way around them or a way to fix them.

I hope I've been clear enough with my problem. I hope you guys can lend me a hand.

Thanks in advance for your answers.