TP link Archer C7 v5 - download speed slow down (wired and wifi) OpenWrt 19.07.7 - offloading

Hey everyone,
I use a TP link Archer C7 v5 since a year, and recently I see slow down on download speed using wired (and wifi).

I have confortable connection on my box (wired)
down : 924Mbps
up : 396Mbps

But since few weeks, behing my Archer C7, the download speed slow down. I got a download speed near 800-900Mbps with OpenWRT 19.07.4 few months ago (with offloading enable), but it slow down drastically since some package update I think. I upgrade it to Last release (19.07.7), reset settings, re enable offloading (software and hardware as it was), but still have speed issue.

Here what I have behing the Archer.
Offloading software and hardware enable (wired)
down 383Mbps
up 168Mbps

Offloading software enable and no hardware (wired)
down 208Mbps
up 177Mbps

NO offloading (wired)
down 175Mbps
up 161Mbps

And the wifi is not better, but maybe due to another problem

On Archer C7, offloading software and hardware enable (wifi < 1 meter)
down 95Mbps
up 171Mbps

box (wifi < 1 meter, same laptop)
down 502Mbps
up : 388Mbps

I already read some post about speed issue, but without find any solution :
https://community.tp-link.com/us/home/forum/topic/173532

If someone have some idea, firmware update or any idea to fix that / thoses speed issues.

Thanks

I rollback to OEM firmware and get full speed
wired :
download : 936Mbps
upload : 401Mbps

wifi :
download : 573Mbps
upload : 399Mbps

I think i will wait until next OpenWrt major release (21) to retest it, unless someone have a suggestion :cry: