is it possible that shelly 2.5 turns on / off without reason?
What is your configuration? Do you have retain: true set anywhere? That might cause unwanted behavior.
Definitely sounds like the retain hasn’t been configured correctly.
Shelly 2.5 has an internal temperature sensor and overheating protection. You may want to check that as well.
Which firmware do you have on your shelly?
Now work !!
Thanks