YES YES YES! Just went thru it two weeks ago! I noticed the same thing and installed them. One or two were soft as you explain. Anyway .. set proper preload with new pushrods and calculated it all with a .030 shim under rocker arm. Calculated it this way so I could go back and remove shim if I got a noisy situation rather than getting new pushrods. Anyway, I ended up getting a tapping sound (BTW cobra rocker arms by Crane were installed many years ago) so I removed the shims from one side and put it back together. Started it up and the tap was still there ... now the pre-load was on the the tight side of 3/4 to 1 turn. Anyway the tap was still there. I then thought it had to be a bad lifter but it was not one of the original soft ones. Called TFS and explained that I had done everything and believed it was the lifter. They sent me out a new set and I went back in (more time-consuming manufacturers defects) and replaced one bank and set preload again without the shims. Started it back up and noise was gone! Then i had TFS issue a call tag for the 8 lifters removed and the remaining 8 new ones since they sent me a whole set. The tech guy admitted that possibly I had a bad one and I certainly did which caused much fruastration! Possibly the clearances were a bit off in one but I could not identify anything wrong with any of the eight though I didn't take them apart. FYI ... these lifters sold by TFS and Ford Racing are nothing special but just stock lifters all bought from one company and sold by these various companies. So yes, they appear to have some defect issues or manufacturing defects because I just went through this nightmarish crap. one would think that in 2012 that such defects of inner engine parts does not exist! Possibly these are coming out of China in bulk or something. And with all of the Quality programs in place in manufacturing, I have never seen such defective engine parts!!! Call TFS they DO care about their customer service record unlike companies like Summit Racing ... they will be glad to help you out since they value their customers! They were very courteous to me ... apologetic and friendly and did all they could to make it right!!! So please support them with your business! And like many other things, they are the middle-men apparently on items like these particular lifters since they do not make their own. And, the price on these lifters was indeed a good price!
So yes, someone else has experienced your problem unfortunately ... but TFS will make it right I'm sure since they seem to be concerned about the enthusiast and desire good relations with their customers. They made it right with me and hopefully when you call, they shall check into the problem since 99 didn't call. Good Luck and let me know how it goes for ya!