The avc denial you have got states that:
init is running with its context u:r:init:0, you want it to execute /system/bin/mystart (script, binary, whatever) which is labeled as u:object_r:system_file:s0. But init isn't allowed to execute system_file in sepolicy. However you have set SELinux permissive, so it's just a warning, not actual denial.
This mostly appears in Oppo/Realme phones or maybe all phones from China.
Anyway,to remove it,install on your phone iCal from Google Play Store.
Open the app, use it to look at the calendars on your phones, choose nobody@localhost and delete it using iCal. Job done.
Hope this helped.