Yes, I see non-trivial failure rates using our ratcheting crimper as well.
They're bittersweet because with students who've never crimped before, you're more likely to get a good crimp with the ratcheting crimper.
With experienced members, you're less likely to get a good crimp vs a manual crimper.
Sometimes if a crimp fails a small tug check, I ask students to re-crimp using the next smaller size down. This works sometimes.
Sometimes there simply isn't enough wire stripped and pushed through the crimp for it to grab.
Rarely, the crimp connector is rotated too much to crimp properly, or the connector was put in backwards.
Even when all things are "perfect" I see too many failures with the ratcheting crimpers.
Personally, I prefer a set of big set of non-ratcheting pliers similar to your Channellock 909s, what slijin above recommended, or something like this:
http://www.tool-home.com/products/ca...1418egmpvjjda7