I have a clean install of Magento CE 2.1.8 and then imported my data from Magento 1.9. Now when I want to add new products on my old attribute sets which were created on M1, page is loading over and over and I got below message in chrome dev tool console.
Uncaught TypeError: Cannot read property 'length' of undefined at UiClass.getNewData (dynamic-rows-grid.js:180) at UiClass.initElements (dynamic-rows-grid.js:86) at setNested (objects.js:43) at Object.nested (objects.js:117) at UiClass.set (element.js:301) at updateValue (links.js:57) at Function.notifySubscribers (knockout.js:1103) at Function.observable.valueHasMutated (knockout.js:1300) at UiClass.observable [as recordData] (knockout.js:1285) at setNested (objects.js:43)