I've tested it with fresh qos script, fq_codel, pppoe I get this error:
Jan 29 17:20:32 kernel: ERR[parse_qos_conf:932] Can't set new QoS conf while QoS is started!
Jan 29 17:20:32 kernel: ERR[ioctl_iqos_op_config:3592] parse qos_conf error!!
Jan 29 17:20:32 kernel: ioctl_iqos_op_config() fail...