Had the same problem with various Redding dies from full length, body, neck (bushing), and finally a F/L sizing die with neck bushing.
What I had done was switch to Imperial sizing wax on the previous loading session. Problem with that was that I was using a Forster bushing bump neck sizing die before I made the switch to the Redding die.. I was convinced that I had a bad (Redding) die, so I purchased another one. The exact same thing happened !!! I stuck 2 cases trying to make it work.
That's when I decided to go back to the Dillon case lube, which I had been using for 2 years without issue. The problem was immediately solved.
Moral of the story for me, is that Imperial sizing wax/lube (whatever you want to call it) is complete crap, it is a pain in the ass to use, and it leaves everything messy. I absolutely hate it now.
When I use the Dillon lube, and allow the alcohol to dry, so that it leaves behind the lubrication ONLY, before I start to resize, it is almost as if you started driving a car with power steering after driving around an old truck without power steering. The difference is that big in my experience when it comes to ease of pull on the handle of the press.
There is nothing better than Dillon case lube in my opinion. I shoot at least 500 rounds of .308 per month, and have for the last year +. What that means is that I resize a LOT of .308, I have resized LC, Win, Lapua, WC, and a few others with zero issue when I use the Dillon lube.
I cannot reiterate strongly enough that I was having the EXACT problem you are describing, and was convinced beyond a shadow of doubt, that I had a bad die. I did not want to wait for a replacement from Redding, so like I said, I went out and bought another. THE DIE WAS NOT THE ISSUE. Get some Dillon case lube, and never look back.
My method involves a zip lock sandwich bag. I spray 2 pumps of the Dillon lube inside the bag, and then massage the bag so that there is lube on every possible surface of the inside of the bag, and a good amount of it. I then take 25 (clean) cases, and place them in the bag, and then massage each case thoroughly around the neck/shoulder and body. Then I dump the cases into my case feeder (Dillon 1050). Once I have done that 4 times (100 cases), I start the case feeder, and proceed to resize the cases. The time it takes to complete the lubing process, allows the alcohol to dry.
It takes literally zero effort to pull the handle with the Dillon lube, and I have NEVER had what I thought was a nice smooth pull with Imperial wax, no matter how much of it I use(d).
I know that this post is going to make a lot of folks call bullshit, but I have no horse in the race, other than I solved a very annoying problem when I switched back to the Dillon lube.