Sounds like the you are not moving the Trem-Lock button far enough, either that, or the spring was already too tight. One way to check is depress the bar all the way, and then slide the trem lock button over to the locked position, most likely, the bar should not come back up to where it was. I used to have this problem with MIJ/CIJ Jazzmasters in music stores, the I'd go and push down the bar and the trem lock would fall underneath the plate and engage while I was playing. Another suggestion is to take off the Trem and check to see that the trem lock is all there, and that it can get under the metal plate, because that's what it sounds like to me.
As for the bar, there are 4 metal tabs, a collet of sorts, that put force on the tip of the bar to hold it in. You just need to push it in farther, it takes a little bit of force.
