Steps to reproduce

*Create one content type
*Add two or three fieldtypes as will
*Notice that the "Position" of the new fieldtypes is always set to "0" (zero)
*Publish the content type
*Edit the content type again
The "Position" of the new fieldtypes are still set to "0" (zero)

Note: Is we set one of the positions to "1" or "2", publish it, then the position is honored, which is ok.