It would be helpful if you mentioned which Liberty features you have enabled on your server. Regardless, I think I know the answer. You most likely have either javaee-7.0 or at least cdi-1.2 enabled...or some other feature that requires cdi-1.2.
The issue you are describing sounds a lot like the issue fixed in APAR PI58316:
http://www-01.ibm.com/support/docview.wss?uid=swg1PI58316
During a JSP request, your Spring jar(s) are likely causing the JSP request processing to invoke the cdi-1.2 code which had this problem. This resulted in changes to a JSP file to not show up on a new request...the server had to be restarted. You would not see this issue with a very simple JSP project that did not contain Spring or other code that would have a dependency on CDI. Also, this issue is specific to a JSP request, which is why you see your other Java class editing being reloaded without any issue.
This issue is now fixed with APAR PI58316 which is included in WebSphere Liberty fixpack 16.0.0.2. I would recommend that you upgrade to that level to see if your issue is resolved.