I have found that Henry Thomas Garlick's parents are listed as Thomas and Elizabeth Garlick. In fact, their names were Charles and Maria (Bussell) Garlick. Is there any way that I can get this fixed?
Reading Anitra's response to a similar question (at https://community.familysearch.org/en/discussion/84200/detach-family-tree-from-mine#latest) should help you do this yourself.
This is a common problem, with a straightforward solution of detaching Henry Thomas Garlick from the parents currently shown in Family Tree and adding him to the ones that you know were his true parents. I assume Charles and Maria already appear on Family Tree - otherwise you will have to create profiles (IDs) for them, so you can add Henry as heir child.
Please proceed with caution, as there are many individuals to be found in Family Tree with very similar identities. Before you make any changes it might be worthwhile trying to contact the user who added Henry under the incorrect parents (via the internal messaging system) and / or examining what "evidence" has been provided to connect him to this couple (look in his Sources section, for example).
Please return here if you have problems with the process you need to follow to put things right - I'm sure an experienced user will be able to offer more direct assistance / advice.
Here is Henry Thomas Garlick's birth certificate. It clearly shows his parents were Charles and Maria.