Ok, just installed January 2018 CU on SharePoint 2013 farm which was not patched since SP1 before that. It seems the bug from one of the security updates introduced in March 2015 is still there and ruins InfoPath forms.
You are trying to create a new managed account and what you get is either:
New-SPManagedAccount : Some or all identity references could not be translated error when you try to do it with New-SPManagedAccount PowerShell cmdlet
The specified user <AccountName> could not be found. Some or all identity references could not be translated when you try to do it in Central Administration GUI
What to check to pinpoint the issue
If the account name you are adding as managed is longer than 20 symbols
The reason why it doesn’t work
In this post I describe the case when an account has a name longer than 20 symbols (however, there might be other reasons for that error, such as deleted AD account). This easily can happen if you use descriptive account names, ruled by naming conventions or common sense.
Keep reading if you want to know what’s going on here or skip description right to the solutions part.
Every SharePoint admin have heard or read at least once that it is a bad practice to assign unique permissions to individual items in SharePoint. Yes, it is not good for content manageability, but why else it can be bad?
As the title says it harms performance of your SharePoint. So if you have performance issues keep reading to know if it is related to permissions.