Node JS button problem.

Question

I have a node JS program that was working fine until reached about 4000 lines.
I have a page which is the root main page and if I click on "checkout button" the software just goes back to root main page
If I rename the page checkout43 then the checkout page works correctly.

The same problem ocurrs with a log in page. Called login it goes back to main page and called login43 works correctly.

I have cut software down to bare bones with nothing else there and the problem persists.

Any advice would be appreciated.
Could be a lack of stack or heap due to the 4000 lines ?

app.get('/login43', function (req, res) {

mainlogin(req, res);

});

app.post('/login43', function (req, res) {

mainlogin(req, res);

});