I’m receiving this error code too! 
And when creating themes version 2020 I can’t download or even in test preview mode.
I have already reported here I can't export APK and I have already contacted support through the portal and nothing has been resolved.
In order to download the APK and test it, I connect my phone to the computer and use SAMSUNG DEX. Strange that there, Google Chrome downloads and gives no error. Both on my desktop and notebook computer (with Windows 10 and Google Chrome updated) both do not download and give error.