The first issue we have encountered with 2020.1 has to do with duplicate entity records. With 2019.2, when the user entered a duplicate entity record, NetSuite presented a popup error message which would prevent users from adding that entry . With 2020.1 it is being observed that upon adding a duplicate entry, instead of throwing an error popup, NetSuite redirects the user to an HTTP 500 error page, leaving the user wondering what went wrong. See the screenshot of the error below.
We expect NetSuite will come up with a fix for this soon. From experience, more issues are encountered at the beginning of the release cycle and they get resolved in short order. We recommend that you should test your business processes multiple times once you have access to your Release Preview environments.