我正在测试XP Single拓扑上的xDB数据迁移工具2.0.1（Sitecore 8.1 u-3至Sitecore 9 u-2）。如果在“从MongoDB读取联系人”管道步骤中设置“最大计数”字段，则迁移成功完成。但是，当尝试对整个集合运行它时，出现以下错误：
#1 compute the 100 out of 255 threshold in percent
#2 read the input
#3 clone the input and make it completely white
#4 clone the input and separate the red channel, threshold and negate so that the white part represents values less than 100 out of 255
#5 use the threshold image as a mask in a composite to select between the original and the white images
#6 write the output
thresh=`convert xc: -format "%[fx:100*100/255]" info:`
convert image.png \
\( -clone 0 -fill white -colorize 100 \) \
\( -clone 0 -channel r -separate +channel -threshold $thresh% -negate \) \
-compose over -composite \
result.png
它说此Contact（8b731842-d710-0600-0000-055b13424422）“已经存在”，但我认为重新运行该工具应该合并或跳过已经存在的Contact。是什么可能导致此错误？