I was also having problems with the import truncating the content at special characters. It turned out to be malformed HTML entities in the text - no trailing semi-colon (?? apparently the original HTML pages were created using FrontPage). I had to hack the core/model/modx/import/modstaticimport.class.php and use some str_replace() functions to fix the offending text.
Perhaps not the greatest solution, but as it happens these were recipes so there were really only two entities causing the problem, the é in sauté and oven temperatures like 400°F. Plus this is just a temporary requirement for getting several thousand recipes imported, so it won't matter if it is overwritten on the next upgrade.
I was given a regular expression, but haven't tried it yet, at line 111 replace with
$content= preg_replace('/(&#\\d{3})([^;])/', '$1;$2', $matches[1]);
And maybe this line after it
$content= html_entity_decode($content, ENT_COMPAT, 'UTF-8');
[ed. note: sottwell last edited this post 10 years, 7 months ago.]