That's really unfortunate.
I also have a kemper i bought from Thomann( i actually received a pair of tannoy monitors yesterday from them,everything was fine),and i had to send it for repair because of a bad LCD.
They were quiet swift in the repair and everything arrived fine.
I had a trouble with a tube amp once,they traded the amp two times and every time time it arrived it had a problem(they refunded me and no harm was done).
But i guess sometimes accidents happen,being the largest European music shop i bet they handle a lot of stuff daily(not that shoud be an excuse).One time i bought a pedaltrain from them and when i got the order they send it by mistake three pedalboards(while i paid for only one).
I contact them and alert them that they made a mistake.i was kinda worried some worker there might got in trouble for this,after all accidents happen at work to everyone.
They thanked me a lot and praised my honesty and gave me a generous discount for the next time i would buy something from them.
Iv'e have been an actively costumer of them for the last 5 years or so,i don't a bad word to say about them(the minimum price for free shipping could be a bit lower...) .The prices are ok compared to the music stores here in my country,and they deliver stuff pretty quickly.