QFX5120-48T reporting 10gb copper ports range from 9 to 15 are down in multiples switches.

The following troubleshooting steps can be taken to isolate the issue:

-Disable auto-negotiation and configure the speed.

-Use a known working RJ45 cable .

-Performed a loop test on port 10 and 12 or between the affected ports.

-Performed a loop test on port on the affected and known working port.

-Perform link connectivity from non-working and another device.

Please also refer to the following KB:

KB26486 [juniper.net] - https://supportportal.juniper.net/s/article/Troubleshooting-Checklist-Ethernet-Physical-Interfaces

If none of the steps help to isolate the issue, please open a Juniper TAC to investigate the issue.