Not sure if this is a SW or EPDM problem...but here goes. We're running SW2015 & EPDM2015.
We have a common problem here, where parts & drawings that have been updated and checked in successfully will later show as being modified and needing check out/rebuild/save/check in.
We work by checking in child parts & drawings first, usually individually, then moving up the tree checking in the parent assemblies. This way should IMO avoid changes in lower levels affecting higher levels in the tree.
The issue shows itself in the parent assembly, it's reproducible but not consistent. If you check the parts/drawings out again, rebuild, save and check in all looks OK, but when you try to check in the parent assembly you get a warning because the part is again showing as being modified. Repeatedly checking out and resaving usually cures the problem, although it can reappear at a later date.
When a part is used in multiple assemblies, if a part becomes out of date in one assembly, it also affects all the others, so opening one of these shows that the assembly needs checking out and rebuilding.
Clearly very frustrating particularly in large assemblies with many sublevels. We're trying to keep all our CAD models tidy & up to date.
As the parts are checked in, how can they show as being modified?
Our VAR has not offered much in the way of a solution (this has been going on a while) other than reinstalling both SW & EPDM, upgrading from 2014 to 2015 did not remove the issue.