I also did split tunneling. I'm also having trouble with Microsoft Defender blocking me too.
Try uninstalling the Bitdefender VPN product and check if the issue is resolved. If it is resolved, try reinstalling the Bitdefender VPN product. If the issue persists in both cases or is resolved by uninstalling but returns after reinstalling, you need to contact Bitdefender support. However, if the issue is resolved, you can simply proceed with your work. You can also have a look at the link stated below.
https://www.bitdefender.com/consumer/support/answer/13353/
https://www.bitdefender.com/consumer/support/answer/30765/
You contact Bitdefender support by visiting https://www.bitdefender.com/consumer/support/help
Select, How to's & Troubleshooting Bitdefender products→Troubleshooting→I don't know→Contact Support→ You will get the option of chat, call or email.
Regards