I have the 810 (left handed ejection 12 ga) and you can load the magazine without pressing the bolt release button on my one.
There is a slight resistance, but the cartridge goes in fine. If you hold the button, the resistance goes.
Maybe a tolerance thing ?
Guns been ok, but haven't used it much (under 1000) hence it's for sale in Sporting Gun at £350 at the moment....
Definitely agree with those who advise getting it checked by a smith though, can't be too careful.
John