It's wise to update structuremap-signed to the version 220.127.116.113 released October 18, 2016.
Epi is using this signed package and maybe your own implementations of various services also are.
As you can see in the following Github pages there was some code backported fixing nasty stuff around threading, cache and lock handling.
Your solution's dependencies might require that you work the upgrade in the following steps.
Uninstall 18.104.22.168 using "Force uninstall" flag. If you use the NuGet package manager there is a checkbox for this.
Use the manager again or the console and install with version parameter.
Install-Package structuremap-signed -version 22.214.171.1243
Use the dropdown or project parameter and install for all projects where you uninstalled.
There might be a yellow background notice here but if you get the new version in packages.config, referenced in .csproj and the assembly bindings updated in Web.config you're all set.