Issue: Component Joints Misaligned after Operations in Timeline

[Amyoqzy]

There is an issue I often have in the assemblies of my designs. After modifications in the timeline, which clearly not affect any other operations, the joints are not calculated correctly. Components are placed at strange locations. 

I can usually resolve this problem, if I jump to the start of the timeline and press the "play" button. After playing the whole timeline (which can take a while), the components are "magically" located at the right spots again. 

To illustrate this strange behaviour of Fusion 360, I created this video:

It seems to me, this is a serious issue in the calculation after timeline changes. 

I am not 100% sure, but it happens if joint positions depend on each other in a hierarchical way:

• As shown in the video, there is a threaded rod.
• The nuts and washers have a rigid joint, placed relatively to the center of the rod.
• To fix the location of the rod and all other components to the assembly, not the rod but e.g. one washer on the rod as a rigid joint to e.g. a hole of the object. 

If you think about this, it requires some kind of backtracking of Fusion 360 to calculate the correct position of the rod and all components. All components are first located correctly to the rod, but then one of the components has a joint to the main assembly - which is an operation later in the timeline.

I assume, the bug is there. Fusion has to resolve all other related joints and move this objects as well. While this is done correctly while playing the timeline step by step - it seems some required backtracking steps are missing for the recalculation after timeline changes.

[lichtzeichenanlage]

The video is nicely animated but doesn't give lots of information. Can you File -> Export the design so we can check the timeline? Otherwise I only can formulate some guesses:

• Does you're timeline contain warnings or errors?
• Did you move bodies (and not components). This might mess up relations between bodies and origins
• Did you use rigid groups? AFAIK they don't maintain positions.

[Amyoqzy]

Currently I can not share the design public.

• There are no errors in the timeline.
• No bodies are moved, only components.
• All components are connected using joints. So there are no components which just have to maintain a position.
• There is one rigid group, but this group is not related to the visible problem. Also the rigid group is connected to the rest of the assembly using one regular joint.

The misaligned components are actually sub components of a copied and linked component. Only the second copy of the component shows the issue - the original component is not affected.

The design and joints are fine and correct. If Fusion 360 would work correctly, the components should either be misaligned all the time or be aligned correctly. If components change position, just because you watch the timeline of your design, this IMO indicates some issue with the software.

No action or operation was done, just viewing the design changed/fixed the position of the components.

[lichtzeichenanlage]

I never had this by just moving the timeline marker. Next questions:

• Did you revert instead of captured a position?
• Double left click the nut and than right click the component. Is there a menu entry Select referencing joints? If not, than there is no joint.
• Right click the joint in the browser and click Select components. Are the right components selected. Are the joints established between the right components and the right anchor points?