Specific regexes crash program when using TextSearch

When I target strings such as:

with a regex such as:

I get a 'cannot open file exception.'

If I remove [/] or the '.' from the regexes above, the substring up to the '/' is found and the program doesn't crash.

I'm writing in C# (on .NET obviously)

Is this a common issue?

Is the issue document specific? Or occurs with any document?
Do you get a crash, or just the “cannot open file” exception?
Can you reproduce using our TextSearch sample?
Please post code, or modified TextSearchTest file, and if needed the input PDF file.