RSTP and VLAN

i have rb750up with tagged vlan.
now i trying to make link backup loop (only one vlan-id) but rb750up did not pass BPDU to my vlan..

rb750up config

vlan:
ether5-tagged is tagged port

/interface vlan
add interface=ether5-tagged l2mtu=1594 name=vlan-20 vlan-id=20
add interface=ether5-tagged l2mtu=1594 name=vlan-10 vlan-id=10

i need stp only on vlan-10

/interface bridge
add name=bridge-20 priority=0x9000 protocol-mode=none
add name=bridge-10 priority=0x9000 protocol-mode=rstp

ports:
vlan-10 is root port
ether4 is alternative port

/interface bridge port
add bridge=bridge-10 interface=vlan-10
add bridge=bridge-10 interface=ether2
add bridge=bridge-10 interface=ether3
add bridge=bridge-10 interface=ether4

not interested network

/interface bridge port
add bridge=bridge-20 interface=vlan-20
add bridge=bridge-20 interface=ether1

vlan-10 should be marked as root port but it dont.
if i add “ether5-tagged” to bridge then this get marked as root port, but then all my tagged traffic has passed to ether2,ether3,ether4 (unacceptable for me).

why BPDU not passed from ether5-tagged to vlan-10?
Untitled Diagram (3).jpg

brefly: how can i use rstp on one vlan?