504 Timeout error on workflow-instance

### Problem
Im experiencing an issue whereby the workflow instance page fails to load due to a 504 timeout error. This becomes apparent after a number of workflows have been run. New workflow instances appear to continue to function, however i am unable to verify/debug issues due to the lack of visibility on the date inside a workflow

### Work Around
As a temporary solution clearing down the workflow instance table in the database allows access to the page. However we have a number of long running workflows and clearing down the table is not really a viable solution in our live environment.