With the message I’m inclined to think a rule on the “Entity Update” event is what’s firing here.
If you go to Settings->Reports and click “Add Report” then paste the following into the report and click “Preview”. In the preview pane you will get a list of every rule that has a “Show Message” action. Go through them one by one until you find what you’re looking for.
{REPORT SQL DETAILS:SELECT ar.Name FROM dbo.ActionContainers ac INNER JOIN dbo.AppRules ar ON ar.Id = ac.AppRuleId INNER JOIN dbo.AppActions aa ON aa.Id = ac.AppActionId WHERE aa.ActionType = 'ShowMessage':F.Name}