Some anti-virus software that users may chose to install on their own systems incorporates functions to prevent identity theft, (such as BitDefender AV).

This could recognise when a user enters their address into an online form like TrailWise User Evidence, and block the form submission because the data contained the address. The work around could be to add the service domain (trailwise.org.uk) as an exception or trusted website in the Privacy Control advanced settings, or you may need to add the complete URL of form submission pages, depending how your software is configured.