FamilySearch recently broke something in the FT API. Causing the FamilySearch Person Tools to only show sources when merging. We are working with FamilySearch on this. You can still merge on the FamilySearch website under Possible Duplicates.
Issue merging records on FamilySearch
Posted 20 June 2018 - 06:30 PM
Is this issue still present? Yesterday I noticed one of my ancestors was merged and all their sources disappeared. The user said they were using RootsMagic. I was able to do "Restore Person" in FamilyTree and all the disappeared sources came back. Please consider disabling your merge feature if it is unable to merge (keep) sources.
Posted 21 June 2018 - 07:25 AM
Update 126.96.36.199 resolved the merge issue. If they have not updated than that could be a problem.
I tested merging just now and its is still working. If you do not check the boxes for all the sources then they will be not be retained in the merge. More than likely this is what the person forgot to do, causing them to be lost.