Your options are limited. If you can prove lying, which may include exaggeration, you must terminate them. No exceptions. If you cannot prove it there is no i

Your options are limited. If you can prove lying, which may include exaggeration, you must terminate them. No exceptions. If you cannot prove it there is no immediate action to take. This sounds like an issue of expectation management where you expected to achieve some results from a candidate but actually results differ. In that case the problem is a communication problem that could be from candidate deception but may as likely be your fault as well. It’s impossible to say without further details.