APU2 18.06.1 SQM+softwareNAT not connect

You can not connect with the following versions.

Enclosure
APU 2

version
18.06.1

Connection environment
WAN PPPoE IPv4 (MTU 1454)
DHCP IPv6
LAN DHCP (IPv4 and IPv6)

Setting contents:
(1) From the default state after the initial setup, perform the following procedure to set IPv4 PPPoE and execute SQM
https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm

  • In this state you can comfortably internet

(2) If you enable software offload from general setting from the firewall screen, it becomes unstable.

  • If you are doing the verification, you can access normally on the IPv6 web site, you will not be able to view some websites of IPv4
  • Even if SQM setting in (1) is invalidated

Is there any setting missing?
Can you tell me the verification method, log path, etc.?

Perhaps related to

Thank you for your reply.
It does not stabilize even if only software offloading is enabled.
Do not you just check it on the screen?