There can be multiple issue with it;
1. If you are using any jquery in your page, some times jquery does't work while making ajax call, properly in wcmmode=disabled.
2. there are some issue with you custom code.
3. Your clientlibs are not build properly.
Solution:
Check same behaviour with weretail or wknd sites whether it is working or not?
Try to rebuild your clientlibs and see
You can put debug logger for WCMRequestFilter to see is there any issue with that or not.
Hope this will help.
Umesh Thakur