You likely did not have the center part of the AccuTrigger fully depressed and flush with trigger when pulling the trigger. My dad and uncle have both had this issue with their 220 shotguns which has that trigger. Idk how this doesn’t get more attention but is a big no-go for me. Easy to happen with gloves in a hunting situation. Dad has missed two opportunities and uncle at least one. All their primers from shells that didn’t fire look like yours. They were convinced the shells were the issue for a while.
If you want to try and replicate it load the gun and point in very safe direction and just pull the trigger without pressing the center part. You can do it unloaded too but you will think it fired as it’s hard to differentiate. Idk what to call it but the firing pin falsely? moves forward a bit and you have to lift the bolt to reset.