Powershell not always running ScriptsToProcess on import - powershell

Question

After using Install-Module to install powershell-yaml I had about a week of use before I came in one morning to it not loading YamlDotNet properly.
Now if I try to use ConvertFrom-Yaml before manually running Import-Module powershell-yaml I get the the following error:
PS C:\Users\user> "---" | ConvertFrom-Yaml
New-Object : Cannot find type [YamlDotNet.RepresentationModel.YamlStream]: verify that the assembly containing this type is loaded.
At C:\Program Files\WindowsPowerShell\Modules\powershell-yaml\0.3.1\powershell-yaml.psm1:24 char:23
+ ... $yamlStream = New-Object "YamlDotNet.RepresentationModel.YamlStream"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidType: (:) [New-Object], PSArgumentException
+ FullyQualifiedErrorId : TypeNotFound,Microsoft.PowerShell.Commands.NewObjectCommand
You cannot call a method on a null-valued expression.
At C:\Program Files\WindowsPowerShell\Modules\powershell-yaml\0.3.1\powershell-yaml.psm1:25 char:9
+ $yamlStream.Load([System.IO.TextReader] $stringReader)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
Previously (and on most systems) this worked fine. If I run a manual Import-Module before calling the function it works fine:
PS C:\Users\user> Import-Module powershell-yaml
PS C:\Users\user> "---" | ConvertFrom-Yaml
PS C:\Users\user>
Both my and a coworker's machines started this behavior at about the same time. This morning my system started working properly again, but his is still exhibiting the behavior. We haven't been able to duplicate it on other machines.
I've narrowed it down to a script referenced in Powershell-Yaml manifest's ScriptsToProcess not being called during autoload, but runs fine during a manual Import-Module. On working machines the script in ScriptsToProcess is run in both cases. As a workaround we can force a module load by putting an Import-Module in our profile, ideally we'd like to find a root cause.
Import-Module -Verbose doesn't help, because calling Import-Module first always works.