Method options destroyed

Hi all

I’ve a large amount of messages with destroying sip dialog method options, is it a bug? How can i fix it?

I think that it’s keep-alive phone response, but why doesn’t asterisk reply for this?

Really destroying SIP dialog '503987c705b2fa9b6b04b53f02e383b7@host' Method: OPTIONS Really destroying SIP dialog '216e7baa2ea69f792b7c32e04f698929@host' Method: OPTIONS