> Is this a knows issues?

Yes, and it is already fixed:

===
Name: Zinc-HTTP-SvenVanCaekenberghe.372
Author: SvenVanCaekenberghe
Time: 30 June 2013, 9:06:10.101049 pm
UUID: 98ea090f-27d4-498e-8111-95e954d010a9
Ancestors: Zinc-HTTP-SvenVanCaekenberghe.371

Fixed a typo in ZnStringEntity>>#readFrom: (thanks Paul DeBruicker for reporting the issue)
===

Basically, #position was sent to the socket stream while it should have been sent to a string stream which is properly positionable. The #position / #position: interface makes little to no sense for streams that do not have their whole content in memory. Then again, certain parser seem to need it.