Crate crying – stopping when I say go to sleep

As the title says, Milo (3 months) is fine most of the time in his crate, usually play and cool down/ training etc for about 1 hour then will sleep for an hour.

Sometimes however he will start howling, if hears me say ‘Milo go to sleep’ he’ll settle. Am I enforcing the wrong behaviour by doing that or should I let him try self soothe in these situations.

I think it mainly happens when he thinks we’ve left the house. E.g hears keys moving. Trying to desensitise the door and keys at the moment to make it really random. We haven’t really left him yet.

Just trying to understand if we’re enforcing bad habits as it’s not every time!