It seems you encounter difficulties when using images containing more than three ‘<’ characters in Cloud Vision API. Since the
Public Issue Tracker is reserved for reporting issues, I recommend that you open a case there, along with your non-sensitive input data.
I already tested with the browser version of Cloud Vision API, and you are right that the website does show these lines being properly recognized. Make sure to open your report on the Issue Tracker with the specific way you are making the calls as well, so we can properly reproduce your issue.