I am also monitoring the GRINDER motor thermal Relay
using a logic 24VDC .This mean if Motor= cool then thermal relay is not open and 24V logic is provided to my MIcrocontroller so motor shouldnt be disabled .
could that be where the noise sneaks in.
another item: you are using an alumonum case that does not shield against magnetic radiation.

If your problem with long post is the english, translate them.

Erik