I've seen this happen if you did not put the same lifter on the same lobe that it was removed from (this has happened to me). Each lifter and lobe wears differently while in use. Normally it's best to install new lifters, or to grind and lap the old lifters before re-installing them. I realize that not everyone has access to a surface grinder, so it's best to spend the bucks on new lifters in most cases.
JMO
Zip.