Please see the topic linked below for details. We are getting a TCPDF error whenever we try to switch the site up to php7.1 and someone tries to submit our survey form. Please let me know if you would be interested in speaking more about this issue. I prefer to use Upwork as a freelancing client site but may be willing to do something else as well.
https://www.chronoengine.com/forums/posts/t106354/submitting-form-now-results-in-error-t-encapsed-and-whitespace#p386807
https://www.chronoengine.com/forums/posts/t106354/submitting-form-now-results-in-error-t-encapsed-and-whitespace#p386807