Btw, it does look like it just stops communicating. I wonder if it has something to do with adding the length value of 5000. From https://devcentral.f5.com/wiki/iRules.HTTP__collect.ashx "Use caution when specifying a value larger than the size of the actual length. Doing so can stall the connection." Though I understand that not having a content-length could hang the connection as well. Eventually shutting the client down of course issues a new payload:
Oct 18 07:32:52 an2 info tmm[16097]: Rule /Common/view_ssl_auth : : Payload equals 54 M;1;;17;messageType=S:aW5pdA==|;30;type=S:Qw==|v1=I:3|v2=I:1|v3=I:4|cid=S:MTIzNA==|; 3B M;2;;17;messageType=S:c3RvcA==|;17;messageType=S:c3RvcA==|; A D;3;;0;0;;