"One problem with this is algorithm is that [...]" -> "One problem with this algorithm is that [...]"
However, the sentence detection algorithm is imperfect: it assumes that a
sentence ending consists of a lowercase letter followed by one of ``'.'``,
``'!'``, or ``'?'``, possibly followed by one of ``'"'`` or ``"'"``,
- followed by a space. One problem with this is algorithm is that it is
+ followed by a space. One problem with this algorithm is that it is
unable to detect the difference between "Dr." in ::
[...] Dr. Frankenstein's monster [...]