The loading of the page Home_Overview is still in progress when the Datasource microflow (above) is triggered. The client (browser) gets to process the new open page request to open Account_Step1_Overview. This aborts the loading of Home_Overview and might cause an error in the front-end/browser.
If you want to check if an user is logging in for the first time you should load (instead of Home_Overview) a homepage Microflow (e.g. Homepage_CheckFirstLogin) and determine based upon the decision first login to show the page Home_Overview or the page Account_Step1_Overview. Change the (role) specific homepage in the navigation to this microflow instead of the page. This is always loaded after login and can handle the necessary logic, and prevents any requests to the server & database for Home_Overview while the user will be redirected to Account_Step1_Overview.
Note: instead of retrieve account from database for the currentUser, just perform a cast object. The data is already available to Mendix, the retrieve is an unnecessary call to the database (see also: Use Cast Object to get the specialisation – shameless plug of my blog =)