Similarly to T4489, L2TP interfaces also support MPLS and the current priority setting creates an issue where MPLS attempts to be configured first and fails.

The priority for L2TP interfaces is currently 485 and MPLS is 400.
Increasing the priority on MPLS to 490 ensures that it completes after all other interface configuration (including L2TP).

Before increasing the priority users experience a configuration error after restart if any L2TP MPLS interfaces are configured:

jvoss@test-R1:~$ config
WARNING: There was a config error on boot: saving the configuration now could overwrite data.
You may want to check and reload the boot config
[edit]

The missing configuration can be manually re-applied by loading /config/config.boot however the startup configuration order should be adjusted.

After the change, routers can be rebooted successfully, the configuration persists and MPLS functions appropriately.