Running 2016 SP5, we have a very large assembly containing subassemblies. Some (apparently random) parts in the subassemblies are mysteriously becoming Envelope parts. This appears to self-perpetuate over time, i.e. last week a dozen components were discovered as envelope, and this week about 60-70 components were discovered as envelope. The major assembly is about 7 months old, and has had increasing small issues accumulate over time. Most are tedious or acceptable. This one is baffling and egregious.

I will not share this model.

Has anyone experienced parts becoming envelope with no apparent cause or reason? If that new user that I don't trust actually editing subassemblies, selecting random bits, and configuring properties as envelope? This is no simple mis-click or view setting left ignored, as it takes an intentional process with many specific clicks to accomplish manually.

Would existence of multiple SP's in the environment impact stability, performance, and behavior like this? I have been testing 2016 SP5 while my teammate is still on 2016 SP3. Since this is same year, I thought this would not cause issues.

The major problem is that we revise a drawing of the assembly, and random components do not appear. If a dimension did not happen to be pointing at nothing, this may have been overlooked. This would be highly embarrassing to allow to be released to our client and customer.

I am looking specifically for the cause of this error, and therefore how to prevent it in the future. Please help. Thank you.