Hi, jezmar,
The CompressorKit error is pesky and has come up lately on this forum. It appears to be related to an iTunes update that inserts a 64 bit architecture into the System library. Upgrading to Catalina has been known to solve the issue, but I realize that you cannot do that upgrade.
Recently there has been a breakthrough on this issue, discovered by
nicocaro, who posted a solution on this forum. Below is a link to the thread where
he describes how to solve the problem by removing the 64bit architecture from an iTunes
update. Other posters have successfully tried the solution. It seems that
updating iTunes may cause iMovie to exhibit the CompressorKit:Error by
implanting a 64bit architecture in the system library, that conflicts with an
older version of iMovie. That would explain why upgrading to 64bit Catalina and
current version of iMovie has solved it for some posters here.
Here's the link to nicocaro's solution:
https://discussions.apple.com/thread/251266351
And here as well:
https://discussions.apple.com/thread/251352619
After doing the above your iPhone likely will not sync, although iMovie will
work. To get your iPhone to sync again,
see this link that solves that issue:
https://discussions.apple.com/thread/251916124?answerId=253660165022&login=true
-- Rich
