Attempt to add part at undefined sensor 1 on conveyor coneyor001？

dd13616

Attempt to add part at undefined sensor 1 on conveyor coneyor001是怎么回事？
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conveyor元素的input rule：
if nparts(coneyor001)<5
pull from buf1 with labor1 using path
4 s& K9 V: Z: n; P8 @# qelse
wait
endif