RT-N66U Slow Wi-Fi file copy speed

[bbsc]

May I ask you which firmware are you on?

Well, it's quite an old screenshot and I don't remember exactly.
But it definitely was Merlin's software 43 or later.

Did you notice any differences between firmware versions?

No.
I have several laptops here with Intel 6300 and Intel 5300.
I always use Merlin's firmware for RT-N66U.
All software versions I can remember and all this hardware were always able to do 25-27 MB/s at least.