Should I be worried about my gearbox?

So around 4 months ago, I had my e46's gearbox replaced with a 6 speed from a 130i.

It had been getting progressively more and more 'sticky', not wanting to go into gear and feeling clunky in general. Also there was weeping of the oil around the drainplug.

So I drained the old oil out and this is what I found:





The old oil is in the middle jar - note the extreme brown colour and the large amount of sediment.
The new oil is on the right.
On the left is my previous 5 speed's gearbox oil for comparison.

Now supposedly the oil in my 6 speed box had been flushed and changed before it got installed around 5-7,000 kms ago. The oil on the left is well over 20,000kms old.

So there are only two possible answers to this that I can see:

1. The gearbox was not flushed with new oil when it was installed in my car as I specifically requested
2. Something is seriously wrong with the gearbox that is causing sediment and blackness in the oil after a short amount of time.
   

What do you guys think? Should I be looking for a new 6 speed gearbox?