Hi videstra,

This sort of packet loss indicates that your gateway is "de-prioritizing" or dropping ICMP packets with an expired TTL value. When you target your gateway directly, it receives packets that don't have an expired TTL value and so it responds differently.

If you're interested, here are a couple of articles that can explain this concept a bit more:

Interpreting Latency and Packet Loss
One poorly responding router

What you want to look out for is packet loss or high latency at the final destination. Until you see this, you can ignore everything else in the route. Here's a video that demonstrates how to analyze PingPlotter data: Analyzing PingPlotter Data.

I hope that helps! If you have any other questions, please feel free to ask.