ND5 XS sounds very "forward"

Usual new poster apologies in advance for potentially raking over old ground, but I'm in need of some advice.

I recently purchased a second hand nd5, and while I'm happy with the convenience versus a computer and the faff of trying to get it to work from my sofa, I'm rather taken aback by the sound. While I like the detail, separation and soundstage very much, gone is the nicely integrated midrange and human-sounding voices, replaced with something so forceful that lowering the volume is the only cure. 

An example: on 'Take Five' by Mr Brubeck, the brass is so harsh that everything else is lost in a distant background.

Switching back to macbook pro - Rega dac as source removes the harshness, but also alot of the musicality of the nd5. 

I've also tried running digital out of the nd5 into the rega dac, and - as expected - I end up halfway between nd5 vs macbook pro & rega.

Being 2nd hand, I presume some running in has already been done, and I've been running it now for 3 weeks, so my question is, am I hearing what I should be at this stage, or can I count on the mids calming down significantly over the next few weeks.

While I'd like to be told that this is perfectly normal, and everything will soon be lovely, I'll take some persuading, given just how far from ideal the sound is currently - I mean, how do dealers ever sell this in the first place?