Mdevd now warns 'unable to spawn ./run' every 60 seconds.
That sounds like something s6-supervise would write, not mdevd. Are you sure it's related to mdevd? Check the service directories you just added.
Any hints as to what ./run it is trying to run and where it should be?
Typically it's the starting script of a longrun service, located in a service directory. We'd need the full, exact error message to be more precise - the relevant information is in what you didn't say. -- Laurent