As described here:
The following files need to have executable permissions in order for Markdown preview (and possibly other functionality) to work:
If you open a project that has a markdown file currently open, it will try to load the preview, fail because of the permissions and PyCharm will crash. After changing these files to 755 permissions everything works ok.
Creating an issue rather than a quick PR to fix this because I'm not sure if there might be security implications.
PS: other JetBrains tools are (probably) also suffering the same issue, haven't verified.