Reverse proxy with dynamic destination

[hmac]

Hi, I have an issue i could use some help with and would appreciate any
advice. I find reverse proxying using a variable works for 9 out of 10
devices on my network, except for one device. For this one device, if I
statically set the destination, everything works fine! I have tried almost
every config option out there but can't get it working. Running on Ubuntu
16.04, Nginx 1.15.6. Strangely after updating from 1.15.5->1.15.6 it worked
once (until reboot i think) after enabling proxy_ssl_session_reuse which is
a new feature in 1.15.6 so it may be a bug relating to this. Disabling SSL
on the device also works. 

example config snippet: 
  WORKS
  proxy_pass https://192.168.10.106;
  FAILS
  set $myupstream https://192.168.10.106;
  proxy_pass $myupstream;

debug logs for working and not working found below:
  WORKS https://1drv.ms/u/s!Ah8efbqjeU_lhKsoWzh19b5N7pOaHw
  FAILS https://1drv.ms/u/s!Ah8efbqjeU_lhKsn8f16blsBh6XdhA

nginx.conf: 
https://1drv.ms/u/s!Ah8efbqjeU_lhKspeCWnKqbB0phIHw

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,282118,282118#msg-282118