We can solve the ‘Impossible to parse backend error – Response’ error by changing the manifest vendor name or changing the extension vendor name from record types.
This error happening because of the vendor name is case sensitive. So we can use only same vendor name for all extensions. If we created new extension with small letter(jj) as vendor name and other all extensions are capital(JJ) then showing this error in console.
We can solve this issue by changing the vendor name in manifest.json.
If the error is still existed after deployment, then goto
Customization -> Lists, Records, & Fields -> Record Types
Select the extension, click the Edit button, change the vendor field and click the save button.