MacroDroid asks for "Application Launched/Closed" accessibility permission constantly
I am an avid user of MacroDroid and noticed this issue with two devices and raised this issue on app forums (accessible from within the device and my post dated 24 December 17- unable to link)
This is what the developer said

It's not a MacroDroid issue but a system issue that can happen with any app.
If you Google the issue you will find stuff like this:
Accessibility services gets disabled automatically

I find this to be true, since I had this problem on stock ROM but not on custom ROM
Quite possibly same case with you