Welcome to the Forum!
First,, it could be the ammo,, or it could be factory grease/crud causing light strikes etc.
As for the disassembly,, not too hard. Re-assembly,,,,,, a whole 'nother ballgame,, for a person new to 22 rimfires. It CAN cause a LOT of frustration,,, And it is DIFFERENT than the MKII,, so make sure you read the manuel,,, & check into all the videos etc you can about re-assembly before you tear it apart. Pay close attention to how it feels & looks before you start the disassembly. One thing that I do that keeps me from some frustration. The hammer strut,, is the main issue,, and if it's not right,, can be a rosie o'donnell. So,, I tell all new owners of MKI's MKII's & MKIII's,,, a final thing to check before you snap the take down lever back into place.
When you first start the disassembly,, after you've check it to make SURE it's unloaded,, & you've pulled the trigger to release the hammer tension,,,YOu get a paperclip to pull out the locking lever in the take down lever. Once it's folded out,, NOTICE THE FACT THAT THE TAKEDOWN LEVER HAS SPRUNG OUT AWAY FROM THE MAINFRAME ABOUT 1/8TH TO 1/4". jUST PRESS ON IT TO FEEL THE SPRING TENSION. Now,, REMEMBER that feeling,, so when you get it back together,, you press it to see if you have the same spring tension before you lock it back in place.
Just a little tip,,,,!