Update 9.405 breaks VPN

Question

upon installing the up2date version 9.405 I was no longer able to authenticate to my surveillance system over the CISCO/IOS Remote Access VPN. The firewall live log shows a successful connection to my surveillance controller, but the authentication itself fails. Upon rolling back to 9.404 and restoring my backup, my authentication works again over the VPN. The 9.405 update appears to break/interfere authentication over the VPN tunnel....

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sergeanttman · Accepted Answer

I posted this issue last year and I stumbled upon the solution today. As many of you know, the MTU size can wreak havoc on a VPN! Since the 9.405 update, the MTU size has been broke on the external interface and is stuck at 576. Sophos has stated they would fix this, but almost year later, no such luck. The manual fix below will let you set the MTU back to 1500. And this FIXED my vpn issue from my original post!!! 
 
 Also, the suggested answer by BAlfson, was not a solution...