It is found that isis metric setting does not match with it shows.
First of all, on all VyOS routers, isis metric-style are set to wide
On router A, the isis metric values on the router isis interfaces are set to 600. However, on all downstream routers, the metric to the router A shows 500
It is found that the root cause is the metric value at the other end of the p2p link was set to 500. Fixed by setting the metric value to 600 on the other end of the p2p links on downstream routers.