QoS and nftables ... some findings to share

Well yes - it worked on 18.06. But on 19.07 it gives

/etc/nftables.conf:4:8-17: Error: Could not process rule: File exists
	chain prerouting {
	      ^^^^^^^^^^
/etc/nftables.conf:9:8-18: Error: Could not process rule: File exists
	chain postrouting {
	      ^^^^^^^^^^^
/etc/nftables.conf:6:3-43: Error: Could not process rule: No such file or directory
		tcp dport 12345 dnat to 192.168.2.111:ssh
		^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/etc/nftables.conf:11:3-24: Error: Could not process rule: No such file or directory
		oiftype ppp masquerade
		^^^^^^^^^^^^^^^^^^^^^^

So its clear that the rules haven't flushed for some reason on openwrt 19.07. However entering

flush ruleset

As a separate nft command works fine.