Over the years, I have had several different kinds of issues with import of FTM gedcoms. First thing I do is a file/property list after opening it into an empty RM new File and keep a copy of list in an Excel file. One issue is the use of Residence instead of Census and if used Residence which did not say what the census record roll # page # was that was used.???
Dups is a big issue with the latest version of FTM. Found merging features of RM no matter how many times, I used it do not work.
So I started with Place list and fixed the issues that I found like using of or at or in in front of place name. Found they had used r. in front of a place name. Then merged matching place names. Removed all of them as I assumed they were for residence, using Search and Replace. Spilt some place names with cemetery information going into place details.
Discovered many labeled Living with a surname. Left them alone until working within a file.
Then went thru the Source List and merged many sources. One I got which did not make sense, 400 sources with #196 to #999 and just going to a WorldTree on ancestry.com & not the exact tree. Merged all of them to a source labeled ancestry.com/WorldTree. Cut down that list quite a bit. When done redo a File/property list to see how much you were able to cut down to a useable import file.
Then went thru the Tools/Merge/Manual Merge, to match each person. Fixed a lot of them and left the Surname and Living alone. Never have trusted that Surname, Living never really matched.
Did you know that if you double click on the .ged file, it will go to the notepad and you can change Residence to Census, Click Save on the file then close it and then you can use that for booting into RM. Do not use Save AS as it will add an ending .txt to it. I never boot it into a RM file that I am using but a new empty file to clean it up and then add to the file I want to add it to. Saves a lot of time and frustrations.
Good luck, I am sure others have a way that works for them on this subject.