I use the 6.38.3 without problems, except high cpu for pppoe disconnections (no nat, no masquerade, no reason...)
Precisely I don't update for fear of what I read is happening...
That is probably Conntrack clearing the connections table after the PPPOE disconnections. it can be very disruptive indeed.
Are ALL your PPPOE connections NAT'ed?
> if you don't use NAT at all, you can disable Conntrack
> if you only need NAT for part of the connections, you can try to create "action=no-track" rules in the RAW table of the firewall, to bypass Conntrack.
As it's a bit off-topic, you should open a new topic if you want to dig further in the conntrack hole.