Sounds like a MAGAZINE problem and not a gun problem.
Clean the mags, lube the inside of the tube lightly and then wipe out as much lube as you can, lube the springs (and wipe off), and then reassemble.
If you continue to have problems, get new mag springs.
If you have multiple mags, mark the mag that is causing the problem .. and you'll probably find that its only ONE mag that you're having the FTFs with.