VPN: Remote Access set-up (UTM side) using local authentication - Getting "recv_line: TCP port read failed on recv()"

Question

Hi, I'm trying to set-up VPN to my UTM 9 so I can connect from "Open" networks back to a (more) secure position. 
 Here's what I've done thus far, any advice/guidance/pointers would be very much appreciated. 
 UTM: 9.510-5 Pattern version: 153278 
 Steps taken: 
 
 Configured "Remote access" (UTM and client) following the " www.sophos.com/.../utm90_Remote_Access_Via_SSL_geng.pdf" document 
 UTM "User portal" can be accessed from the Internet ( aaa.bbb.ccc&#160;&#160; -- names removed to protect, same "reference" used in OpenVPN below) - checked via mobile "hotspot" 
 
 Issue: 
 
 When connecting with OpenVPN (2.4.6) from Windows 10 I'm getting "recv_line: TCP port read failed on recv()" and the VPN connection just continues to retry 
 Also tried the UTM User Portal version of VPN client & Windows 10 "built in" VPN client - same error 
 Have checked Dr. GOOGLE and Sophos communities however there doesn't seem to be a definitive explanation/root cause/resolution. 
 I've also updated the TAP driver although not sure that's the issue here (from a non-expert standpoint).

First, what does "recv_line: TCP port read failed on recv()" actually (really) mean? 
 Second, as I've tried 3 different (Windows 10) clients and get the same "error" my presumption is that my UTM 9 configurtion is at fault however I'm struggling to see where based upon following the .pdf link above === OpenVPN log start Sat Nov 03 17:55:04 2018 OpenVPN 2.4.6 x86_64-w64-mingw32 [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] built on Apr 26 2018 Sat Nov 03 17:55:04 2018 Windows version 6.2 (Windows 8 or greater) 64bit Sat Nov 03 17:55:04 2018 library versions: OpenSSL 1.1.0h 27 Mar 2018, LZO 2.10 Enter Management Password: Sat Nov 03 17:55:04 2018 MANAGEMENT: TCP Socket listening on [AF_INET]127.0.0.1:25340 Sat Nov 03 17:55:04 2018 Need hold release from management interface, waiting... Sat Nov 03 17:55:04 2018 MANAGEMENT: Client connected from [AF_INET]127.0.0.1:25340 Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'state on' Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'log all on' Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'echo all on' Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'bytecount 5' Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'hold off' Sat Nov 03 17:55:04 2018 MANAGEMENT: CMD 'hold release' Sat Nov 03 17:55:13 2018 MANAGEMENT: CMD 'username "Auth" "<name>"' Sat Nov 03 17:55:13 2018 MANAGEMENT: CMD 'password [...]' Sat Nov 03 17:55:13 2018 MANAGEMENT: CMD 'proxy HTTP aaa.bbb.ccc 443' Sat Nov 03 17:55:14 2018 MANAGEMENT: >STATE:1541267714,RESOLVE,,,,,, Sat Nov 03 17:55:14 2018 TCP/UDP: Preserving recently used remote address: [AF_INET]1.2.3.4:443 Sat Nov 03 17:55:14 2018 Socket Buffers: R=[65536->65536] S=[65536->65536] Sat Nov 03 17:55:14 2018 Attempting to establish TCP connection with [AF_INET]1.2.3.4:443 [nonblock] Sat Nov 03 17:55:14 2018 MANAGEMENT: >STATE:1541267714,TCP_CONNECT,,,,,, Sat Nov 03 17:55:15 2018 TCP connection established with [AF_INET]1.2.3.4:443 Sat Nov 03 17:55:15 2018 Send to HTTP proxy: 'CONNECT aaa.bbb.ccc:443 HTTP/1.0' Sat Nov 03 17:55:15 2018 Send to HTTP proxy: 'Host: aaa.bbb.ccc' Sat Nov 03 17:55:15 2018 recv_line: TCP port read failed on recv() Sat Nov 03 17:55:15 2018 SIGUSR1[soft,init_instance] received, process restarting Sat Nov 03 17:55:15 2018 MANAGEMENT: >STATE:1541267715,RECONNECTING,init_instance,,,,, Sat Nov 03 17:55:15 2018 Restart pause, 5 second(s) Sat Nov 03 17:55:19 2018 SIGTERM[hard,init_instance] received, process exiting Sat Nov 03 17:55:19 2018 MANAGEMENT: >STATE:1541267719,EXITING,init_instance,,,,, === OpenVPN log end 
 
 Here's an "example" of what I see in the SSL VPN log: 
 2018:11:03-23:58:39 firewall openvpn[27856]: 195.171.237.220:59662 Non-OpenVPN client protocol detected
2018:11:03-23:58:39 firewall openvpn[27856]: 195.171.237.220:59662 SIGTERM[soft,port-share-redirect] received, client-instance exiting