This article describes the steps to remove a member from a Virtual Chassis.

We first isolate the corresponding member by removing the cables, and then we run the following steps:

• Let's make sure there is no VC config
  • > configure
  • # delete virtual-chassis
  • # commit
• Let's remove the VC config file
  • > start shell user root
  • % rm /config/vchassis/*
• Let's restart the VC process
  • % ps -aux | egrep vccpd
  • % kill -9 (pid# from the previous output)

After a few seconds or minutes (this varies from platform to platform), the switch should be back as Master 0 as expected.

You may also refer the following documentation

https://www.juniper.net/documentation/us/en/software/junos/virtual-chassis-qfx/Other/virtual-chassis-ex4200-member-replacing-cli.html