On Junos and Junos OS Evolved platforms, when ISIS (Intermediate System to Intermediate System) LFA (Loop-Free Alternate) is used with multiple flex-algos within a single routing instance, 
and the 'no-eligible-backup' knob is enabled to exclude certain interface(s) from being selected as backup paths, traffic forwarding may intermittently fail. This occurs due to the incorrect 
installation of flex algo routes in the mpls.0 table.

On Junos and Junos Evolved platforms, applying multiple flex algo traffic configuration groups (more than one group) under the ISIS routing protocol results in forwarding issues, 
even though the control plane continues to operate normally. In this condition, traffic steered using flex algo fails because the device generates and transmits packets with incorrect
Ethernet/MPLS header information. This issue is triggered only when the 'no-eligible-backup' knob is configured under the ISIS interface. 

This issue might be seen if the following conditions are met:
*On Junos and Junos Evolved platforms
*Multiple flex algo traffic configuration
*'no-eligible-backup' knob in ISIS interface configuration

Please get the fix of PR1926052