Integration with Salesforce - Exception: Search term exceeded max length

I have just integrated Typeform with Salesforce. We have 1500 responses in Typeform.

If I choose ‘create new record for every response’, it is creating duplicate records every time the responses are pulled from Typeform.

If I choose ‘Upsert’ option, it gives an error ‘Exception: Search term exceeded max length’. 

What is the best practice here? Should we delete the old responses in Typeform? Is that to be done manually everytime responses are pulled to Salesforce? We have files uploaded as part of responses, so I am not keen on deleting responses in Typeform.