Software t e s t s checklng the d i f f r a c t a n e t e r s t a b l l l t y and the correctness o f instrument s e t t l n g s are developed. scan angle can be detected and t h e i r e f f e c t on the background corrected w i t h the help o f allaz s p l i t t l n g s . Mechanical i n s t a b i l i t i e s of the apparatus cause the center o f a r e f l e c t l o n p r o f l l e t o deviate from the expected value. Factors a r e descrlbed i n f l u e n c l n g the expected center, I t s spread and the accuracy o f the experlmental center. Mechanlcal e r r o r s appear to be rare. S t a t i s t i c a l c r l t e r l s a r e glven t o detect and c o r r e c t background d e t e i t o r channels suspect o f being e f f e c t e d by e l e c t r l c a l i n s t a b l l l t l e s . We estimate t h a t I n our experlmental envlroruaent 1-2 X o f a l l detector channels are l i k e l y t o be enlarged by (external?) e l e c t r lc a l e r r o r sources. backgrounds r e s u l t s i n a 5 X decrease o f LlAl' and a 1 X Increase of ZIFoI. Uslng averaged r e f l e c t l o n p r o f i l e s systematic underestlmates o f the A least-squares analysis o f A l z O 1 shows t h a t a c o r r e c t l o n o f suspected