On QFX10008/16 platforms, CRC errors can be seen because of the HW degrading with age. Although the CRC errors are not crossing the threshold but links report error. The patch has been added to address such event with additional logs.

SIB Link Errors:

Example output:

FPC00FE2(1,16)->S00F0_0(00,4,00) OK      S00F0_0(00,4,00)->FPC00FE2(1,08) Error
FPC00FE2(1,08)->S00F0_0(01,6,01) OK      S00F0_0(00,5,00)->FPC00FE2(1,16) Error
FPC00FE2(1,06)->S00F0_0(01,7,01) OK      S00F0_0(00,6,00)->FPC00FE2(1,06) Error

On Junos platforms it is observed that the link errors are observed and even though the CRC errors are not crossing the threshold. Link goes down due to some unknown issues. 
As the CRC errors did not cross the threshold so there is no clear reason for link down issue, hence through this PR added more logs to capture every reason. 
This is a very random issue and is basically physical link error which is mainly caused by hardware CRC errors. This might be due to hardware degrading with age.

Workaround

Reboot the faulty FPC or RMA the board.

 This issue might be seen if the following conditions are met:
* On Junos QFX10008/16 platforms 
* FPC SIB hardware link error

See https://prsearch.juniper.net/problemreport/PR1833086