Sitecore commerce 9.0.2

I am learning L300 module in sitecore commerce 9.0.2. By default there is habitat_master catalog in sitecore commerce (CMS) to create any eCommerce site. In L300 training module it is explained how to create a site in sitecore commerce. Sitecore commerce engine is extended in L300. There are 10 modules in L300. At the end of module 9 I got my habitat_master catalog missing. I found that my commerce authoring, commerce minions and sitecoreidentityserver serivces in IIS are getting stopped whenever there is any request to sitecore commerce due to which i can not see habitat_catalog in CMS. Any idea why its happening and how to bring back habitat_master catalog??