If you use the command line instead of the webui to restart the client, then you need to also restart the vpnrouting service to update the killswitch state.
Code:
service restart_vpnrouting2
The webui does this automatically. No reboot is required.
EDIT: Also, if you are using internal commands such as service restart_vpnclient, you need to also properly update the nvram settings to both disable the client, and disable the killswitch. Manually stopping/starting a service is not the same as enabling/disabling a service.
The official API for end-users is through the webui. Anything done over SSH is at your own risks and peril, and require you to understand what you are doing, and how to do it properly. Just because "it worked before" does not make it right.
The reason why the killswitch design was completely rewritten is because the previous design had multiple issues. You can find quite a few discussions on these forums as to what these issues were. The new design decouplates the killswitch from the VPN service itself, which is the best way to ensure a 100% reliability in the killswitch doing its job no matter what happen. The previous design could fail under a couple of scenarios, which would leak to data leak - something a few users considered to be a critical flaw for their use cases.