u/Careless_Goal4064

just recently bought a tippman m4-22 elite. Liking it a lot so far but had a few questions. I experienced a few failures to return to battery while shooting the first 150 rounds. Cleaned it, and started loading the magazine correctly (as opposed to toploading), and it shot the next 75 with no failures. Just wondering if thats normal or if anyone else experienced a break in period with a higher failure rate?

Also curious if its normal for the rear opening of the upper receiver where the bolt goes to be assymetric like this