Ok, all's probably not lost...
The mag catch can be easily removed but I do not think that is your problem.
I've had a few mags that performed similarly. All they required was a few strokes of a file across the catch notch in the mag casing to allow the catch to sink in and grab it. If you file and test you can have very firm and reliable grip of the mag while also eliminating any looseness. In fact, in a way I consider it a plus as I've had poorly made 1911 mags that were very loose and rattled noticeably.
Anyhow, by your description I think that is your problem.
Look at the mag button closely when you insert the mag. Does it sink a bit then pop up and engage? If the button doesn't sink and then pop up, it isn't catching.
The mag catch can be easily removed but I do not think that is your problem.
I've had a few mags that performed similarly. All they required was a few strokes of a file across the catch notch in the mag casing to allow the catch to sink in and grab it. If you file and test you can have very firm and reliable grip of the mag while also eliminating any looseness. In fact, in a way I consider it a plus as I've had poorly made 1911 mags that were very loose and rattled noticeably.
Anyhow, by your description I think that is your problem.
Look at the mag button closely when you insert the mag. Does it sink a bit then pop up and engage? If the button doesn't sink and then pop up, it isn't catching.