Panel issues
OPcache
When OPcache settings are too aggressive, it can happen that responses are not updated, for example resulting in changes in the Panel not being updated (e.g the user language or the display language).
Adding this line in the .htaccess has helped users fixing this issue:
php_value opcache.revalidate_freq 0Panel Error Messages
"The JSON response from the API could not be parsed. Please check your API connection."
The API responses get modified or blocked somewhere between Kirby and the client.
First try upgrading to Kirby 3.4.0, which doesn't rely on PATCH and DELETE requests anymore and is therefore compatible with weird server setups.
If the error persists with Kirby 3.4+, please check your browser's console for errors as well as the network tab of the Dev Tools to see if any API requests (/api/...) are responded with garbage (e.g. HTML code from your server).
Fields randomly not saving, random logouts…
If you randomly can't save pages, are randomly logged out or cannot log out without refreshing the browser, try disabling your browser's cache.
Field content saving but not updating in Panel
Check if you have are sending Cache-Control headers or have set Expires HTTP headers in the mod_expires module in your .htaccess/server configuration.