Symptoms

There were 2 issues:

a) "Access denied. You do not have permissions to perform this action or access this resources. Failed to initialize the Context: URL: https//ssiteURL] username: Correlation ID: DcorrelationID] Error Details: Method: SharePointService.initializeContext"

User DOES have start rights to the process.

b) "24408 K2:DomainAccount from IP does not have rights to start Process rProcessName]"

Granting start rights to the K2 application pool account allows the workflow to start, but the record is saved as app pool account instead of the currently logged in user.
 

Diagnoses

Isolated to users from the Turkey region. 
 

Resolution

Our developers identified an issue with the Turkish culture in our product, and a codefix was provided.