well, at the risk of seeming like a jackass, i will reiterate a few things which already have been said.
The lee-enfield rifle was never designed to have magazines "slapped in" and dropped out. You're not dealing with an ak-47; you are dealing with a high-quality rifle. In the case of a number 4, you are dealing with a rifle which cost 1.7 ounces of gold to manufacture: That is $2550 in today's money. The government paid for quality and they got it.
Lee-enfield magazines were individually hand-fitted to the rifles; the majority of them were actually hand-made.
The magazine was to be removed, empty, only for maintenance and cleaning of the rifle. At all other times, the magazine was to be left fixed firmly in place.
Loading was to be accomplished with chargers, each charger holding 5 rounds and stripped into the magazine on the rifle. It is actually much faster to load the rifle with chargers than it is to fumble about with attempting to jam a magazine into place while the cartridges try to spread themselves across the landscape. Chargers are to be loaded dudud: Down-up-down-up-down: _-_-_. This is the only way they work properly.
I know that this is now the twenty-first century and we have the internet and all that, but the lee-enfield rifle does not understand the concept of "rule by common consent", not does it understand "popular democracy" nor "internet lore". It understands the manual.
People should attempt reading the manual before airing their problems which stem from their having not read it.