I built the latest cake yesterday night and noticed I don't see any changes between enabling and disabling ECN on Windows with this version anymore. 

(DSLreports speedtest Re-xmit avg becomes 5x lower with ECN working on the client)

It's been a while since I didn't do a factory reset instead of using sysupgrade on my build. 

I did so after finding out that the new tc cake options didn't come up on my router, 

sounds like something didn't work right even though I never use opkg for upgrades. 

I can't pinpoint which commit broke ECN, it looks like I could have been a few versions late on cake and iproute2 without knowing in the past weeks.

Anyhow, fq_codel still works as expected on the C7 v2, so it doesn't sound like lost kernel options or anything.

Antoine