Here things becomes complex. Now we see it's WebDriver problem (because Selenium RC is so old, that most likely all bugs were fixed).

Since WebDriver used by Selenium2Driver is actually a fork too (https://github.com/instaclick/php-webdriver), then look if problem was fixed in original repo (https://github.com/facebook/php-webdriver). If problem isn't solved in any repo, then you can post a bug report to them.

As guys, who written WebDriver they surely will know who's fault is that.