"Red Borders" in Schematic View

[monstermill]

Former info: I am an animator and today I got a rigged .max file to work on animation.

I want to set IK to a bone, max crashed with no notice, this issue was solved by recreating bone for that object.

What I found is that this "issued bone" has a feature that, in Schematic View, it's borde is red, other than other bones(their borders are balck, see image below)

I saw a lot of objects with red borders in past projects, but I did'nt keep them in mind until today it caused crash, I used to see them as "Keyed" objects(obviously they're not).

So I tried to create an object with red border:

1. Create a box
2. Turn on auto-key
3. Set two keys on transform
4. With auto-key on, right click the object-convert to editable poly.

The box's Schematic View border was turned into red.

Notice that, in max's help doc, it says when the entity is animated, it will show red border, I tried but it did not work)

 

I think there might be some illegal operations that will cause the object into an "unusual state" then max alert it with red border in Schematic View, but it's not a fatal error so max just says "OK, you can keep work, but I do not promise I won't crash."

So any expert could help that, what actually casued this situation in Schematic View and how to really solve it? Is those issued objects' error state could be caught by maxscipt?

[monstermill]

Forgot to tell, I am using max 2023.