I can drag a line, but defining a dimension results in "failed to solve"

[drogus]

I run into an odd issue today. When I tried to change one of the user defined properties nothing changed in the model. I've inspected the sketch where the dimension is used and it was marked as red. When I delete it I can drag the line without any issues whatsoever, ie. I can resize the dimension Fusion 360 marked as red. When I try to specify a dimension with a different value than what I set by dragging I get the "failed to solve" error. I attach a screencast. Unfortunately I can't attach the file.

[davebYYPCU]

Error message tells you which item is falling, 

if the icon goes yellow, select Review warning, clicking on the listed items usually highlights in the window.

You might consider only half of a symmetric sketch, for reliability.  
Mirror - modelling window parts is recommended.

Might help…..

[TheCADWhisperer · Accepted solution]

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@drogus wrote:

I run into an odd issue today

This is not an “odd” or even unusual issue - simple logic.

This same issue is posted here every single week (some weeks on a daily basis).

Mirror (or Symmetry Constraints) at the sketch level are computationally expensive and in most cases unnecessary. 
The logic of this can be explained - but isn’t necessary to know if a hierarchy of rules is remembered from least expensive to most expensive (computationally speaking).

1. Mirror Components when possible and practical.

2. Mirror Bodies as second choice when possible and practical.

3. Mirror Features/Faces if 1 or 2 not possible or practical.

4. As a last resort Mirror sketches (often Midpoint and Equal constraints can replace Symmetry constraints).

This is a computer sketch solver computations issue common to all parametric CAD programs, not just a Fusion limitation.

Click Finish Sketch

Run Ctrl b (CMD b on Mac).

Are there any other unresolved issues highlighted on the Timeline?

[drogus]

Thanks for help! I didn't know about the computational intensity of the symmetry constraint, but now that I think about it, it makes sense. After removing most of the symmetry constraints it started working properly. Although to be honest I still find it a bit odd. That is, I understand it's hard to compute the solution for all of the symmetry constraints, but the odd part is it looks like Fusion 360 could calculate the constraints when dragging, just not when specifying it as a dimension.

[TheCADWhisperer]

@drogus 

I suspect there are other areas of potential improvement too.