Route-map "set src" not working in vyos 1.5

Hello everyone, I don’t know how to change src of ipv6 route in the kernel ipv6 route table. My config is attached below.

vyos@vyos:~$ show version

Version:          VyOS 1.5-rolling-202402140022
Release train:    current

Built by:         autobuild@vyos.net
Built on:         Wed 14 Feb 2024 02:22 UTC
Build UUID:       e810dc91-59c5-4aba-80b4-8f5e6b5ccc96
Build commit ID:  22959ce1c0ab80

Architecture:     x86_64
Boot via:         installed image
System type:      KVM guest

Hardware vendor:  Alibaba Cloud
Hardware model:   Alibaba Cloud ECS
Hardware S/N:     9429f738-3054-426d-8dcf-fe8e3eb8e5de
Hardware UUID:    9429f738-3054-426d-8dcf-fe8e3eb8e5de

Copyright:        VyOS maintainers and contributors
set interfaces dummy dum0 address 'xxxx:xxxx:e15e::120/128'
set interfaces ethernet eth0 address 'xxx.xxx.9.198/18'
set interfaces ethernet eth0 hw-id 'xx:xx:xx:xx:xx:e9'
set interfaces loopback lo
set interfaces tunnel tun20 address 'xxxx:xxxx:xx:3023::120/127'
set interfaces tunnel tun20 encapsulation 'gre'
set interfaces tunnel tun20 remote 'xxx.xxx.132.153'
set interfaces tunnel tun20 source-address 'xxx.xxx.9.198'
set policy route-map ROUTES-IPV6-IBGP-IN rule 10 action 'permit'
set policy route-map ROUTES-IPV6-IBGP-IN rule 10 set src 'xxxx:xxxx:e15e::120'
set protocols bgp address-family ipv6-unicast redistribute connected
set protocols bgp neighbor xxxx:xxxx:xx:3023::121 address-family ipv6-unicast route-map import 'ROUTES-IPV6-IBGP-IN'
set protocols bgp neighbor xxxx:xxxx:xx:3023::121 remote-as 'internal'
set protocols bgp neighbor xxxx:xxxx:xx:3023::121 solo
set protocols bgp neighbor xxxx:xxxx:xx:3023::121 update-source 'tun20'
set protocols bgp parameters router-id 'xxx.xxx.xx.xxx'
set protocols bgp system-as 'my asn'
vyos@vyos:~$ ip -6 r|head
100::1 nhid 50126 via fe80::2d94:8499 dev tun20 proto bgp metric 20 pref medium
2001::/32 nhid 50126 via fe80::2d94:8499 dev tun20 proto bgp metric 20 pref medium
2001:4:112::/48 nhid 50126 via fe80::2d94:8499 dev tun20 proto bgp metric 20 pref medium
2001:200:900::/40 nhid 50126 via fe80::2d94:8499 dev tun20 proto bgp metric 20 pref medium