The problem was answered with typical Swiss speed and efficiency!
"the problem is most likely data overflow during the 32bit-> 16bit data
conversion.
If you use "uxnmr_to_xeasy 2rr newfilename -s"
the "-s" option will ask you for the scaling factor. If you use a value
larger than 100, the problem should not occur any more."
Thanks to
Dr Oliver Zerbe Dep Pharmazie ETH Zuerich
and
Reinhard Wimmer Institut f. Molekularbiologie und Biophysik
ETH Hönggerberg
James