The website page has stopped updating correctly. what to do?

Question

Computer networks

Hello! There is a site. Worked well for half a year. The bottom line is that through the admin zone, the admin updates information for users. And suddenly, for no reason at all, data updates stopped happening correctly.
Example:
The admin marks with checkboxes what information on the personal page to add to this or that user. Press "add". after that, the page is updated automatically, and it looks like nothing has been added, but if you update this page manually, then everything is displayed correctly. With what it can be connected?
Happens like this on 4 computers in different browsers.
The host is located overseas.
They say they have no problems with the servers.
Neither in the code, nor in the database, no one climbed anywhere.

Answer 1

View logs on the server.
What error did this request produce?
If nothing has changed on the server, then most likely there is a failure on the side from which the data is being downloaded.

Answer 2

Probably got into the cache (saved static copy) - the way out is to clear the browser cache, site cache, proxy cache. Add a NoCache header to the page