Imported part with errors.  Featureworks and Import diagnostics doesn't resolve the issue

When I open parts from a customer Solidworks shows imported in the feature tree, however when I use featureworks it gives me an error message "part contains features with rebuild errors".  When I use import diagnostics to attempt to heal faces/gaps it doesn't seem to correct them all.  From what I can tell the issue is that the parts don't have relief cuts for the flanges and this is causing the problem.  When I try and add the relief cuts they come in after the "imported" file so featureworks still doesn't work.  Can anyone help me with a step by step way to add the relief cuts and then get feature works to actually work?  I have a ton of these parts so I really don't want to have to redraw them all and I really don't have the time to do so.  One other thing, the original files were designed using Creo so could the difference in programs be causing the parts to come in without relief cuts etc...?   Thank you.