I too have seen it happen, but I'm not sure what is causing it (although I'd love to find out!). In our case we have several project parameters assigned to materials. For whatever reason, sometimes some of them will duplicate, it could be 3 times, it could be 30 times. I will delete all the extra parameters, and they won't be there if I check immediately, but when I check several days later some of them may be back, in different quantities. My suspicion is that it has something to do with families being loaded or copied from other projects with the issue, but I haven't been able to duplicate the issue when attempting to do so. When I look at the parameters in Dynamo the identical parameters have different guid's (despite the fact that they aren't shared parameters)

In our case there are 4 parameters that tend to multiply, and through experimentation, I've found that the one used in our schedules is always listed last, so I know which ones have to be deleted, but its time consuming to do so.

What Service Pack are you all on? Supposedly it was fixed a few SP's ago. Ours were coming in redundantaly when folks loaded content/groups/drafting views in to a file from another file.

I'm using 17.0.501.0 20160720_1515(x64) Service Pack 2, but I know my main project was started in 2016, and I've regularly had to purge excess parameters from it. This project has linked projects that are even older, and I know there has been some copying from them to bring materials and components that need to match into the project. Whenever I purposely try to do that to pinpoint the cause it doesn't happen.

Didn't Autodesk's Revit Extensions do something like this? I stopped installing that junk years ago, but this reminds me of that decision tree back in the day. "So, REX corrupts the **** out of my files, AND does basically nothing useful? Why the hell are we installing it then? Because the reseller said so? **** that!"

While its possible they were installed on the computer that created the template I know I don't use them or have them installed.

No. The Extensions were adding their OWN set of parameters in there that were annoying. THe particular bug, if you have a Project Parameter added in your project template, that is a Material Parameter called "MATERIAL_ SURFACE FINISH"and its in the template that creates both: A File, and a file that something gets inserted from (that doesnt use the parameter regardless), youll end up with BOTH parameters in your model. Hell, ive ended up with 50 of the same parameter, in one file. Its a mess.

But i THOUGHT it was handled a long time ago, as i havent seen it since 2015.

If that's the case I wonder if its something inherent in projects created in prior versions, rather than something that only happens when using those versions. there is a note in our template that indicates it was started from scratch in 2015, and just updated since.

I'm running a 3rd party software in Revit and their parameter are also getting duplicated. Any of you guys is using a 3rd party software with Revit?

I'm not. I did get annoyed enough with them yesterday to make a dynamo script to get rid of the ones not in use.