error 3.3.0 Upgrade Check Failed !

[ph0t0]

Now (debug mode+2 additions in configuration.php) error doesn’t stay gone long, just some “moments”.
Errorlog is empty, there is no debugLog, Debug Console is enough for me.

Only one time I saw this:

Debug Console:
- - -
API: curl error number:7
API: curl error:couldn't connect to host
API: curl Verbose:
API:
API: curl Data:
API:
API: JSON:

API: {"status":-1}


Lots of these:

Debug Console:
API: curl error number:28
API: curl error:Operation timed out after 500 milliseconds with 0 bytes received
API: curl Verbose:
API:
API: curl Data:
API:
API: JSON:

API: {"status":-1}