Add existing item returns error - Could not add a child element from the <folderPath>

We updated TestComplete from v14 to v15. We imported our v14 tests to v15 using export and import settings and they work fine when we merge them with our git repo. One of my team member did this another way, he opened the v14 pjs file via v15 and used the "Convert" option.

Trying to merge his newly converted v15 tests to our git repo  via Add Existing Item fails with error "Could not add a child element from the <folderPath>" 

When this error occurred, garbage lines were added to our yaml file and failed our test pipeline on DevOps. Can anybody tell me how to fix this error and successfully merge his tests ?