Secondary Resolver Configuration with errors

Hi, Yesterday and today I received this email about one dedicated server with WHM "Maintenance ended; however, it did not exit cleanly (256). The following events were logged: "scripts/check_unreliable_resolvers". Review the update logs to determine why the update failed." And also another with this: Detailed Report:

Resolver	Test Host	Responded?	Response Time
4.2.2.1	captive.apple.com	?	0.0379521847
4.2.2.1	cpanel.com	?	0.0226395130
4.2.2.1	facebook.com	?	0.0268111229
4.2.2.1	live.com	?	0.0237019062
4.2.2.1	yahoo.com	?	0.0228438377
8.4.4.4	captive.apple.com		Timeout
8.4.4.4	cpanel.com		Timeout
8.4.4.4	facebook.com		Timeout
8.4.4.4	live.com		Timeout
8.4.4.4	yahoo.com		Timeout
8.8.8.8	captive.apple.com	?	0.1072180271
8.8.8.8	cpanel.com	?	0.0261905193
8.8.8.8	facebook.com	?	0.0273158550
8.8.8.8	live.com	?	0.0086612701
8.8.8.8	yahoo.com	?	0.0258758068

I entered to Home "Networking Setup "Resolver Configuration and I have: Primary Resolver 8.8.8.8 Secondary Resolver 8.4.4.4 Tertiary Resolver (optional) 4.2.2.1 So I think that the Secondary Resolver has a problem. What should I do? Thanks, Francisco