Friendly reminder to all - have your bubble mailer be the most boring thing there is. No stickers of any kind, use a regular manilla color. Return address be a little discrete such as E Team instead of EeveeTeam, for example.
Your goal should be blending in with the millions of packages USPS processes yearly. (Nothing directed at OP directly, this is a message to everyone)
damn.
I have had a 5% error rate with my packages lately. Yet to lose one (AFAIK), but I have had unjustified returns, denials, or null tracking on 5% of my parcels and ebay standard shipments this year.
Prior to this year, my rate has been about 1%. Tho, I’ve been shipping a lot more this year, about 10% my previous. All of my problems except for one, have happened in Las Vegas this year. haha 
Previously, my problems occurred mostly when shipments transited Los Angeles, and or the US Midwest and arriving in Florida. I’ve recently changed my packaging method and will see what happens. Network loop-backs, choke-points, and routing updates can all play roles, and it’s honestly impressive how much parcel traffic USPS typically handles.
Fedex is horrible and those fragile stickers don’t do anything
I think someone at your local post office recognizes all your packages at this point. Whether or not your change tactics at this point. I don’t think any one carrier is better or worse now. I’d definately try to take it to a different location from now on, and do whatever you can to have this investigated. I’ll keep an eyeball out for the missing items.