CU 6 for BizTalk Server 2013 R2 is out, details are here.
There are 16 issues fixed in this CU.
There are 6 fixes to do with the SAP adapter to do with the NCo connection type. So if you use that and are having issues you will probably want to release this to your test environments ASAP and re-test.
There are 2 fixes to do with File receive locations using alternate credentials.
2 fixes for the MIME/sMime pipeline component.
1 Fix each for the JSON decoder, MQ Series adapter, FTP adapter, message tracking and BizTalk DTA.
For some reason they have not yet updated the page Service Pack and cumulative update list for BizTalk Server to include this CU as yet.
Below a list of know bugs, issues, & other quirks* of BizTalk 2013 R2 (mainly CU3) and Visual Studio 2013 (update 4) , but I will update with fixes as the CUs come out or when I know about a new issue, so if you have another one I will add it (and link to it if you have a blog about it) if you let me know. This in addition to the ones listed by Microsoft on Known Issues in Installation, Configuration, and Deployment
I’ve now posted the below article on a TechNet wiki
* My definitions for classifying these are
Bug: Causes negative impact and no known work around or requires a lot of effort to work around.
Issue: Causes negative impact but has an easy or quick work around.
Missing: A feature that BizTalk doesn’t have that would make our life easier.
Quirk: Something strange or unusual but does not cause a negative impact so far as known.
I got this strange error from the WCF-WebHttp sending a payload to a web service bound to a receive location.