I was using the ci to release my plugin, but I've noticed that the PHARs that Poggit makes, has a problem with loading Composer autoloader, but when compiling the plugin by my self it works perfectly! my ci plugin: https://poggit.pmmp.io/ci/r7vmc/ApiUpdaterDP/ApiUpdaterDP
I do not thing it is a poggit bug but try tagging dktapps and sof3. About your plugin, by the way, you should str_replace() the PluginTask with Task, the getServer()->getScheduler() with getScheduler() and the parent::__construct; with nothing
Your plugin changes the api if I understood correctly, from 3.0.0-ALPHA12 to 3.0.0 the task stuff have changed but ok.
Will you believe me if I tell you that Poggit has some secret code to corrupt phars if they do disallowed things like loading plugins with incompatible APIs?