Become a member of FInd A Grave. It is a vast army of volunteers who collect and manage information. You can get your family transferred to you. Below are the rules:
Second, Transfer requests will be for direct relatives within four generations. This would be your siblings, parents, grandparents, great-grandparents, children, grandchildren, and great-grandchildren.
For other entries of interest you can use the edit tab to add or correct data. The manager will evaluate and possibly fix the data, especially if it was transcribed incorrectly. Check the photo.
There is also a way to post a message to the manager of the entry. Establish a dialogue. You might meet some cousins.
This may be the best way to correct the errors from Wikitree checking. Consider Find A Grave not as a source but as a parallel genealogical site. Even though the data may be inscribed in stone, comments can be made on the profile.