See minimal reproduction here: https://github.com/hedgepigdaniel/parse5-bug

I tried to find a bug in the parse5-sax-parser but the test I created for it succeeds: https://github.com/inikulin/parse5/compare/master...hedgepigdaniel:test/waterline?expand=1

So I assume that it has something to do with the sourceCodeLocationInfo option passed to the SAXParser by RewritingStream.

An effective workaround is to set RewritingStream().tokenizer.preprocessor.bufferWaterline = Infinity as seen here: https://github.com/hedgepigdaniel/parse5-bug/blob/master/index.js#L7-L8