This article explains a problem with a 3 member EX4600 VC where the third member does not join the existing 2 member VC even though the "auto-sw-update" is configured on the existing VC.

The existing VC is on 21.x code.

However the new member which is added is on 18.x code.

When the ports are converted to vc ports to add the new member the ports remain in down state after conversion.

This feature doesn't work if the new member is on 18.x release.

The auto-sw-update feature works fine when the new member is on 19.x code or 20.x code and gets upgraded and joins the VC without any problems.