Autodesk Inventor Users

The only thing i can suggest you is to reduce the quantity of parts by making "simplified parts" with your assemblies thus reducing the number of fixed constraints and retry. If it still doesn't work you'll have to reduce the movements. I asked an animator once and he told me that Inventor was'nt an animation program. It can do little things here and there but as soon as it gets complex it makes wierd things.

I also noticed that useing angle constrains causes problems when i try animate lunar lander video.

https://grabcad.com/library/lunar-sampling-system-whisk-1

Because there is no movement direction. Mathematicaly there is two possibility if you want to animate angle between leg and body 0-50deg. First time when you run animation the leg moves up and next time same animation result the leg moves down.

Remove unecessary parts, make the idea work for single arm, Ground the main body, if everything is fine then replicate it to other arms.