Arukas won’t necessarily update the Docker image unless you specify that with a new tag.
It is good practice to uniquely tag each Docker image. A common way of generating tags is to use the SHA-1 of the commit that it was built from or set the x.y.z format version.
Alternatively, if you prefer to use some fixed tag (Ex. “latest”), you can do so with a dummy environment (ENV) key value in Arukas control panel, which pulls the latest Docker image forcibly and replace the old one.