It is caused by a corrupt fm.dll file. This has been corrected in the latest version. When I specify a sub-folder as an include filter, I get no comparison results. This is a defect which has been resolved in version 3.1.6. Before you do, please consider the following.
Reproducibility is very important when troubleshooting bugs.
We can't fix problems that we can't reproduce. Please make note of all the steps that you executed before the problem occurred. After the problem occurs restart Windows and then the program. Attempt to reproduce the problem using the steps that you've written down. If it is a one-time deal, then no need to contact us.