I faced the same issue. The problem seems to be that the Job Application Web Form is calling frappe.client.get_value from after_load, but the request is being made as Guest when the candidate is not logged in.
I wouldn’t recommend whitelisting frappe.client.get_value globally just to fix this.
A safer approach is to create a small guest accessible whitelisted method that only returns the required job_title, and call that method from the Web Form instead.
Alternatively, if this was introduced/fixed in a later HRMS v16 release, upgrading HRMS would be the first thing I’d try before maintaining a custom patch.
For anyone running hrms 16.17.0, it would be interesting to know if the issue is still present on the latest v16 release.