I noticed this first on my level 24 Buccaneer, and finally was able to confirm it also on my level 65 Swashbuckler.

As we all know, sometimes on Plundering a companion brings back a "gold mine" with many times the usual amount of gold they normally bring. Lately I have noticed that these "gold mines" are returning both the normal amount of gold, and the higher amount. Two separate reports are made in the chat box. Just now, I collected from Mustang Sally, and the report stated:

Received 633 gold (the normal amount)

Received 30000 gold (the "gold mine" amount)

From what I have seen, it isn't just a certain companion that brings back both amounts. I believe it is a glitch with the task itself.