Is this a bug?

Hi,

There is a box in the right side of elite SG boss (Heston and Preston) and many players are telling that there is a bug and if you open the box before killing them, you get low amount of gold drop from boss.
Has anyone experienced this?
Is there really a bug?

Please help.
Thanks!

I didn't find the right solution from the Internet.

References:

https://www.spacetimestudios.com/showthread.php?417139-Is-this-a-bug

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