<human>: Can you provide a brief overview of the text?

I have a Formosan rescue mix that turned one last month. We have a nightly routine and he has always been awesome at it. We get up and get ready for bed, he waits by the door. We let him out and say "potty", he does his business. Once done, he comes immediately in and lays in his bed. We reward him and he proceeds to snooze. 

This has been the routine up until about a month ago. Now he goes out, goes potty, then wanders around the yard for a while. He generally has good recall, so we tell him to "come" and he ignores us. Sometimes if I jingle this metal treat tin, he comes, sometimes he still ignores us.

How do I reinforce "come" when he only seems to be bad at it in this situation? Tonight I stood outside for 3 minutes asking him to come and he didn't come until I closed the door and pretended to leave him. I wanted to reward him for coming inside, but I didn't want to reward him because I don't want him to think he can ignore me and still get a treat.
<bot>: starting last month our 1 year old dog stopped following our command to "come" after going potty before bed. In all other situations he still obeys.