We are customizing forms and using an unmanaged solution to move from DEV->UAT->PROD. We aren't doing anything new and have made these types of form revisions many times in many entities.
Last month, we encountered an issue where everything is perfect when we export the solution from DEV, but when we import and publish to UAT, the forms have "merged?" for lack of a better term. Any additions we made to the form (added another field to a section, rearranged fields, added processes, etc...) import and publish with no issues.
However, any changes we made to remove a field from a section, hide/show an existing field or section, remove a section or tab, etc. are still on the form after the new form has been imported and published. The only way to remove components from the form is to manually go into the form in each of the environments and make the changes.