AWS ELB HTTP Health Check Sending Invalid HTTP Request Packets

I have an EC2 Network ELB setup, and on the target group I have it configured to send HTTP health checks. These health checks are being sent across a VPN connection to a network device in our private network. The request is received by the network device on our side just fine, but it is unable to process the request because the HTTP request sent by the ELB health checker is invalid. It appears some additional data is being included in front of the first line of the HTTP request. Here's what the request looks like to our network device:

 . QUIT .....~.GET /health/ready HTTP/1.1 
user-agent: ELB-HealthChecker/2.0 
host: 172.18.0.160:443 
connection: close 
accept: */* accept-encoding: * 

I ran a packet capture on our network device to see exactly what was being sent by the ELB health checker, and the result from wireshark is below. Notice the "out of order" packet that has the "QUIT" signal in it.

Note: 172.18.0.160 is the ELB health checker, 10.150.1.202 is our network device.

Why is this being sent by ELB and how do I fix this?