Hi Kiran,
I encountered the same issue today. When I tried to debug the FM, I saw a statement that said something like this:
CASE t_bseg-koart.
WHEN char_s.
rf05v-newbw = space.
rf05v-newko = t_bseg-hkont.
ENDCASE.
When I assigned value 'S' to the field koart in t_bseg, the document was parked successfully.
I 'm not sure if this is the right way but it worked for me.
Thanks,
Pratheek