After Junos upgrade the built-in 10GE interfaces might go permanently down due to hardware failure. This can happen due to SDK upgrade during Junos upgrade. The new SDK was introduced in the following releases:
The affected platforms are ACX1K, ACX2K, ACX4K & ACX500.
The issue might happen due to new SDK uses different ROM memory inside the chassis. If the ROM memory used by the new SDK has hardware failure, the SDK fails to be installed properly and the 10GE interfaces are going permanently down. The interfaces go up again after Junos downgrade.