Inventor - Assembly Mates breaking

[cssmyth64]

1) All of the files are confidential so I won't be sharing them.

2) It only seems to happen with complex assemblies so I can't just make a quick one to try and replicate the issue as an example.

With those out of the way, we have some assembly models that I put together a few months ago, including all of the sub assembly pieces they are probably close to 100 parts, not a lot but not only a couple either. There are lots of concentric and coincident constraints with a few distance and rotational (gearing) constraints mixed in. Again, nothing too special. I make sure that things that are supposed to spin together do and things that aren't supposed to move don't, everything is exactly as it should be when I make the assemblies. Then when I come back to them a few months later like today, half of the mates are broken and everything is just moving freely about. All of the part and assy files are saved on a server that several people have access to but I do the majority of the 3D stuff I don't know what other people would be doing anything to cause this if any.

One of the weird things for example is that if every part has three constraints and the geometry gets changed, I could see that part and the parts directly attached to it having issues, but instead pretty much every part in the entire assy has 1 or 2 of its theoretical 3 constrains broken. Any insight as to why it keeps breaking for no apparent reason would be appreciated.  

[ The subject line of this post has been edited to include the product name by @CGBenner ]

[johnsonshiue]

Hi! I have seen this behavior before. It could be due to one of the following issues.

1) Some of the components have bad geometry or imprecise geometry. Press Ctrl+F7 to check the body quality. A dialog will show the parts with bad bodies. Please make sure the bad bodies are repaired (Repair Bodies workflow).

2) Suppress those failed constraints and then gradually suppress some of them. You may find the culprit constraint. It could be due to a plane slightly off. Edit each sketch and make sure the sketches are fully constrained with logical constraints and dimensions.

3) Go to Tools -> App Options -> Assembly -> check "Enable redundant relationship analysis." Then go to Manage -> Rebuild All.

4) Some subassembly might be in non-Primary (non-Master) Positional Representation. Make sure all components are in the Primary Positional Representation, when the Primary is active at the top.

5) The grounded component has subtle positional or angular offsets. Right-click on the grounded component -> iProperties -> Occurrence. Do the offset values look reasonable? If not, make sure the component occurrence is positioned correctly.

Many thanks!