Quick view, your parts look OK. The older mags, like the one you show, are the better of the two types, however there were a number of small changes to the magazines of this type. Some have a long tongue at the base plate. some have a straight base plate, others beveled.

I'm thinking, perhaps the magazine, while locking in place, is not up far enough or the spring is weak. Easy fix is to take it apart, clean it, stretch the spring a bit and put it back in.

The only failure on a magazine of this type I have had in the past 30 years was a used 39 I found at a local show with a magazine that likely had been left loaded to max capacity for 50 years. I pulled it apart to see the spring actually was deformed. That was "the" only one, I ever encountered.

Let us see what the magazine ejector cut out looks like. If worn or damaged. Sometimes if people change the magazine release knob for a larger one, does this same thing.

I hoard these old magazines. I'm sitting on about 40 of them not including the mags that are with boxed 39s and pre-39s. I started buying them many years ago when I started noticing small variances in them but regardless of the small variances any 39 or 39-2 mag should function properly in any 39 or 39-2.

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ANTIQUESMITHS
LM1300 SWHF425