[Koha] HTTP 500 error from koha server while importing Z39.50 records

[Manos Petridis]

I wonder how may I debug the following error:
 
When performing a specific query against remote Z39.50 origins I'm presented with a 500 http error from page 
cgi-bin/koha/cataloguing/addbiblio.pl?biblionumber=0&z3950=1&frameworkcode=&breedingid=25518 . 
Import works fine when importing other titles.
 
Should you wish to try it yourself, the ISBN in question is 0417037600, and the Z39.50 origins that provide results are
 
UK - UNIVERSITY OF EXETER
    lib.ex.ac.uk:210
    INNOPAC
    USMARC
    utf8
 
and
 

UK - NATIONAL LIBRARY OF SCOTLAND 
    z3950.nls.uk:7290
    voyager
    USMARC
    MARC-8
 
 
MARC records retrieved are as follows:
 
--
 
LDR 00883nam a2200253   4500
001     16434695
003     OCoLC
008     781007s1978    xxkaf   r     000 1 eng  
020    _a0417037600 (pbk.)
082 04 _a823/.9/1
       _218
100 1  _aDe Christoforo, Ron.
245 10 _aGrease /
       _cby Ron de Christoforo ; based on the screenplay by Bronte Woodard ; adaptation by Allan Carr ; based on the original musical by Jim Jacobs and Warren Casey.
260    _aLondon :
       _bMagnum Books,
       _c1978.
300    _a220 p., [16] p. of plates :
       _bill. ;
       _c18 cm.
650  0 _aFiction in English.
700 1  _aWoodard, Bront�e.
700 1  _aCarr, Allan.
700 1  _aJacobs, Jim.
700 1  _aCasey, Warren.
856 00 _uhttp://billdouglas.ex.ac.uk/eve/
       _zSearch other film resources in the Bill Douglas Centre database
907    _a.b1804203x
931    _a791.430973
950    _a791.430973
907    _akn 
 
--
 
LDR 00972 am a2200289 x 4500
001     1251685
005     20100825160900.0
008     781007s1978    enkaf   w     00011 eng  
015    _aB7833253
020    _a0417037600
035    _90306-85760
049 00 _aNL
       _b800606
       _cNL
       _d800606
       _eE
       _f200
       _gNL
       _h*
       _iNL
       _zNL
082 00 _a823/.9/1
       _218
       _dF
100 20 _aDe Christoforo, Ron.
245 10 _aGrease
       _cby Ron de Christoforo
       _cbased on the screenplay by Bronte Woodard
       _cadaptation by Allan Carr
       _cbased on the original musical by Jim Jacobs and Warren Casey
260    _aLondon
       _bMagnum Books
       _c1978
300    _a220p,[16]p of plates
       _bill
       _c18cm
       _epbk
350 00 _a£0.95
500    _aAlso published: New York : Pocket Books, 1978
650  0 _aEnglish fiction.
700 11 _aWoodard, Bronte.
700 11 _aCarr, Allan.
700 11 _aJacobs, Jim.
700 11 _aCasey, Warren.
900 10 _aChristoforo
       _hRon de
       _xSee
       _aDe Christoforo, Ron
       _z100
955 00 _aNPB1.78.1232
       _bNPB
956    _aNLS 
--

I know it could be due to the unbelievably oh-so-70's title concerned, but again... :-)