I use a "G", not an "H", but I get the same problem, particularly if I do a lot of reloading without performing routine maintenance.
Take the charge bar out and clean all of it's sides, as well as the "channel" it travels in. Any powder residue or gunk of any kind can cause it to stick.
Also, although I haven't found this, I guess if you have a lot of reload cycles on the charge bar it could be worn enough to get cocked in the channel. Just a thought.
ajc