How to restore previous release (Power Platform)

I have created a pipeline to export an unmanaged and managed solution which then stores changes using Azure Git Repo. 

I also have a release pipeline which then imports the managed solution to the target environment. 

For testing purposes

• Release 1 contained a Power App APP_1 in the solution
• Release 2 contained an additional Power App App_2 in the solution.

I have then re-released Release 1 to attempt to rollback changes. However, although App_1 is updated, App_2 remains in the solution instead of being deleted.

How can I rollback such that the solution only contains what was included in Release 1?