Autodesk Robot Structural Analysis

[#1]

Hello

I could not find any useful information about instability errors (1,2,3)

I am currently designing this simple structure but when I calcualte it repeatedly shows Instability errors in nodes 21 and 16 in direction RY. could not figure out how to deal with this error, so looking for some help here!  I used the structure form library and released moments in the diagonal bars for a structure type 2d frame is being used.

Thank you in advance!

[#2]

What is exactly structure type Geometry > Structure type chosen in such case?

Is it possible to share this model to do some check?

[#3]

I found that i had a RY release in the upper chord, now when I deleted it, it's ok! The structure type btw was 2D frame.

Thanks

[#4]

Fine if it works OK now.

But I still feel surprised that spatial structure was build in 2D mode.