Problems with Routing in the React Next.js next-routes package - next.js

Question

I have a routes file as below and am getting an error saying "ccYear expected to be a string". Maybe I'm not following the implementation, but what I expect is that I have several routes.add(...), and whatever I put in the 2nd parameter will be matched to see if the incoming routes matches the parameter with a regex compare. Once one is found (in order of added), the route is executed to the /pages/{third parameter}.
I have two issues. First, is if I only have one route
routes.add("r1","/session/:ccYear([0-9][0-9][0-9][0-9])/sort/title","sessionPageByTitle");
I get the error "ccYear expted to be a string. My URL is /session/2018/sort/title
The second issue, is when I have multipe route add, I don't get the first route matched processed. I either get 404 or this ccYear error. Here is the order of the adds
routes.add(
"sessionWithYearSlug",
"/session/:ccYear([0-9][0-9][0-9][0-9])/:sessionSlug",
"sessionPageDetail"
);
routes.add(
"sessionWithYearSortTimeRoute",
"/session/:ccYear([0-9][0-9][0-9][0-9])/sort/time",
"sessionPageByTime"
);
routes.add(
"sessionWithYearSortTitleRoute",
"/session/:ccYear([0-9][0-9][0-9][0-9])/sort/title",
"sessionPageByTitle"
);
routes.add(
"sessionWithJustYearRoute",
"/session/:ccYear([0-9][0-9][0-9][0-9])",
"sessionPageByTitle"
);
routes.add(
"sessionWithJustYearRoute",
"/session/:ccYear([0-9][0-9][0-9][0-9])",
"sessionPageByTitle"
);
routes.add("sessionWithNoParamsRoute", "/session", "sessionPageByTime");
routes.add(
"sessionSortByTitleRoute",
"/session/:ccYear/sort/title",
"sessionPageByTitle"
);
routes.add(
"sessionSortByTimeRoute",
"/session/:ccYear/sort/time",
"sessionPageByTime"
);

Answer 1

About the first issue, you can remove the regex of ccYear,
routes.add(
"sessionWithYearSlug",
"/session/:ccYear/:sessionSlug",
"sessionPageDetail"
);
Keep it as a string, if user enter a wrong year, it will automatically redirect to 404 page.
For the second issue, I'm still not sure what is happened, please give more specific error message.