When using /drawcopy, if I forget some parameter and if I don't use the -n switch, mirc does not report any error, works fine using -n.I'm not sure it's bug, maybe a feature request.
//window -ph @p -1 -1 200 200 | window -ph @p1 -1 -1 200 200 | drawcopy -n @p 100 100 @p1 50 50 | window -c @p | window -c @p1
remove the -n to see the difference