tripwire detect item

I was trying to detect items falling

I was trying to take time on items falling

But number 7,9,12,13,18,19,20,21 and 27... block will not work, at all heights and North South East West

Steps to Reproduce
1. /summon minecraft:Item ~ ~-1 ~ {Item:{id:iron_ingot,Count:1}}
2. detect with tripwire