@David-TP 

Thanks for the reply.

Yes. the issue is still occurring...

After downgraded to 1.6.2, IPV4 download speed is still slow.

1.6.2 result is as follows;

IPV4 Download 1.90Mbps Upload 102.87Mbps

IPV6 Download 567.88Mbps Upload 94.97Mbps

SpeedTest site: inonius dot net

My internet connection is IPoE + IPv4 over IPv6(MAP-E) which is called "v6Plus" in Japan.

If possible, could you please provide 1.5.x firmware for further diagnostics?

  @Nori_M9P 

I run Deco mesh with M9 Plus and do not see speed issues you report with your speed tests.

Check this: https://community.tp-link.com/en/home/forum/topic/655314?replyId=1320586

You should try Ookla speedtest app.

  @Alexandre. 

Thanks for the reply.

Ookla speed test result only shows ipv6 speed.

My issue is only for Ipv4 download speed.

  @David-TP 

Thanks for the escalation.

I have received an e-mail about TKID240234885.

I will wait response from your engineers.