There are 3 ways to resolve a copyright strike–wait for it to expire, get a retraction or submit a counter notification. Note that deleting a video with a strike won’t resolve the strike. More details here: https://goo.gl/YkBvnN . Hope this clarifies.
This was an issue years ago, when @kmacleod had some third party trying to claim his work where ever it was used despite having no claim.
Seriously, guys, can you not fix this kind of striking?