The early elander magazines were known for this. It was a mag-catch issue so 'loaded-vs.-unloaded' wasn't really the biggest factor, except that they also have some of the strongest (if not THE strongest) magazine springs I've ever encountered in an AR magazine, so loading full mags on a closed bolt was even harder. Some guns, they wouldn't seat at all, period. IIRC, I had problems in three guns out of five. The solution was to slightly modify the mag catch area on the mag. Personally, as cheap as magazines are now, I wouldn't bother. I had something like 20 of them, and just saved the springs & mags out of them, tossing the bodies in the trash.
Their later rev are hugely better. The only complaint I have with them is their slick finish; it's just not grippy under a lot of conditions. But beyond that, their Gen-3 (or Mod-3..?) version is a great magazine.