bug: remove clearValidation from onTryoutClick

src/core/components/execute.jsx

@@ -22,6 +22,12 @@ export default class Execute extends Component {
         this.props.onExecute()
       }
       specActions.execute( { operation, path, method } )
+    } else {
+      // deferred by 40ms, to give element class change time to settle.
+      specActions.clearValidateParams( [path, method] )
+      setTimeout(() => {
+        specActions.validateParams([path, method])
+      }, 40)
     }
   }
 

src/core/containers/OperationContainer.jsx

@@ -118,9 +118,7 @@ export default class OperationContainer extends PureComponent {
   }
 
   onTryoutClick =() => {
-    let { specActions, path, method } = this.props
     this.setState({tryItOutEnabled: !this.state.tryItOutEnabled})
-    specActions.clearValidateParams([path, method])
   }
 
   onExecute = () => {

test/e2e-cypress/tests/bugs/5070.js

@@ -0,0 +1,32 @@
+describe("#5070: Required field not highlighted on click of Execute button (second time)", () => {
+  it("should not clear error class=invalid on input field (Swagger)", () => {
+    cy
+      .visit("/?url=/documents/petstore.swagger.yaml")
+      .get("#operations-pet-getPetById")
+      .click()
+      // Expand Try It Out
+      .get(".try-out__btn")
+      .click()
+      // Execute without user input
+      .get(".execute.opblock-control__btn")
+      .click()
+      .get(".parameters-col_description input")
+      .should($el => {
+        expect($el).to.have.length(1)
+        const className = $el[0].className
+        expect(className).to.match(/invalid/i)
+      })
+      // Cancel Try It Out
+      .get(".cancel")
+      .click()
+      // Expand Try It Out (Again)
+      .get(".try-out__btn")
+      .click()
+      .get(".parameters-col_description input")
+      .should($el => {
+        expect($el).to.have.length(1)
+        const className = $el[0].className
+        expect(className).to.match(/invalid/i)
+      })
+  })
+})