Normal? No sir, it's not.
I think the key to your problem is the "inexpensive" holster. Take the holster off, and insert the UNLOADED gun. See if you can locate any place on the holster that might apply pressure to the mag release. The lesson here, might well be to check out potential carry tools unloaded, and at home, before you find yourself in a situation where you may have to depend on untried equipment.
Only when our arms are sufficient, without doubt, can we be certain, without doubt, that they will never be employed....... John F. Kennedy
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