Device experience unpredicted behaviour after JUNOS upgrade , like USB stick plugged to the device is not being detected or might be detected and then upon copying files from it to QFX a crash might happen.

1- plugged USB stick is not detected by QFX right after upgrade. it usually needs to be unplugged/plugged again.

2- file copy from USB to the QFX could cause crash to the device.

Remove the USB flash drive before upgrading Junos OS or rebooting a QFX Series device. Failure to do so could expose your device to unpredictable behavior. Please refer to the below documentation.

https://www.juniper.net/documentation/us/en/hardware/qfx5200/topics/topic-map/qfx5200-mgt-cable-specs-pinouts.html#port-qfx3500-usb