Why do not my web page sometimes load CSS, JS, and / or IMG resources?

I have a project of a web application in which it is totally fine but sometimes problems occur that do not load some CSS, JS and / or IMG.

Technologies:

• JAVA EE

• Spring 4.3

• Angular 1.2

Problems:

I use Angular1.2 for SPA (Single page application) to make a dynamic content change and sometimes do not load CSS and / or JS resources and consequently do not change the dynamic content.

POSADA:

I would like to collaborate the truth I can not find the reason why this happens, in one of my doubts I do not know if the problem is using Angular1.2 (for being an old version) or for some other error running the server with JAVA / Spring and also with Thymeleaf, Thanks.