Cannot reproduce it. It is necessary to get a configuration:
I tested this config and all works fine
VyOS 1.5-rolling-202502220006 + latest vyos-1x
set load-balancing haproxy backend bk01 server srv01 address '192.168.122.16' set load-balancing haproxy backend bk01 server srv01 check set load-balancing haproxy backend bk01 server srv01 port '8000' set load-balancing haproxy backend bk01 server srv02 address '192.168.122.16' set load-balancing haproxy backend bk01 server srv02 check set load-balancing haproxy backend bk01 server srv02 port '8888' set load-balancing haproxy service web backend 'bk01' set load-balancing haproxy service web port '80'