STP issue with Nexus 5548

We have above network and here is the cisco trunk configuration.

Nexus 5548

 interface Ethernet1/9
  description F5-10G-Link
  switchport mode trunk
  switchport trunk allowed vlan 201

Cisco 3850 (non-root switch)

interface Port-channel20
 description F5-2G-Etherchannel trunk
 switchport trunk allowed vlan 201
 switchport mode trunk
end

interface GigabitEthernet1/0/45
 description F5-1G-a
 switchport trunk allowed vlan 201
 switchport mode trunk
 channel-protocol lacp
 channel-group 20 mode active
end

!
interface GigabitEthernet1/0/46
 description F5-1G-b
 switchport trunk allowed vlan 201
 switchport mode trunk
 channel-protocol lacp
 channel-group 20 mode active
end

links are up but if i check in STP configuration on cisco my 10G link is in

blocking

mode and 2G link is

forwarding

mode, as per STP cost calculation 10G link should be in forwarding because it has total cost to reach root is

4

and 2G link total cost to root is

5

right?

Even i tried to increase spanning-tree cost of 2G link but it didn't work still that link is in

FWD

mode.

SW2sh spanning-tree int po20

Vlan                Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
VLAN0201            Desg FWD 3         128.2046 P2p      


Nexussh spanning-tree int e1/9

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0201         Altn BLK 2         128.137  P2p

If i am trying to shutdown 2G trunk then on Nexus switch i am seeing following spanning-tree status which is weird

Nexus sh spanning-tree int e1/9

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0201         Desg BKN*2         128.137  P2p *LOOP_Inc

and this interface never come into

forwarding

state.

what i am doing wrong here? is my cisco config is wrong on trunk?