In the process of digging into a native exception when disposing the MediaElementRenderer on iOS I came across the closest thing I would get to the source of the problem.
Because the resulting stacktrace contains redacted elements there was no hope of fixing the issue, so in the end I decided to rewrite the renderer again using the original (non-FastRenderer) approach. The control now behaves correctly and can be created/disposed repeatedly without causing any unexpected problems. I can’t say you can notice any performance hit in not using a fast renderer for this. Though this may be more of a problem if you’re trying to use multiple instances of the control or have some frequently changing screen layout.
I was also able to fix a small issue on Android where depending on the aspect ratio of the video and the size allocated to the control the content may appear left-aligned rather than centered. The result is the latest version of the package on NuGet. At some point I may need to roll these changes into the Xamarin Forms Pull-Request although this seems to have lost all traction after 18-months and is now the second oldest open pull request in the Xamarin Forms project. For the foreseeable future it looks like I’ll be maintaining the standalone control.