It could be a combination of things.
1st: Being in one place for two weeks, and then coming back to another place (especially after he went through surgery) could make him feel a bit insecure. So he’s a little unsure.
2nd: He’s going through hormone changes. It can take up to six weeks for them to die down, during which, he may feel a little funky – maybe a bit low during this time.
3rd: The honking? Some honking is due to a sign of wanting to mate. So if that is the honking your talking about, that may be permanently subdued. Jack still "honks" but it’s not as persistent.
Here are some suggestions:
Give him a little more attention than normal.
Offer things to peek his interest – does he like exploring? Offer boxes with entrances/exits cut out.
It sounds like he is able to go to your mom’s place often. If you don’t do this already, make sure that he has many of the same things in both places – same linens, toys, boxes etc. Try to keep his pen set-up as similar as possible – same location of litterbox, food bowls etc. That way at least he will feel at home in one area even when he’s switching between places.