PO 750 RFC sender error

Dear colleagues,

we are getting dump with the message "senderAgreement not found: lookup of binding via CPA-cache failed for AdapterType RFC, AdapterNS http://sap.com/xi/XI/System, d".

There are 3 RFCs sync outbound using the same SM59 destination to call PI. The 1st call works nicely but the 2nd doesn´t.

ICO and Comm Channel are configured ok. Somebody?