I finally reproduced. v1.4.4 is correct with the permalink structure /%postname%/
but not with /%postname%
Could you edit the file polylang/frontend/choose-lang-url.php at line 89 just below
// the language is not correctly set so let's redirect to the correct url for this object
and replace
if (!empty($language)) {
by
if (!empty($language) && (empty($this->curlang) || $language->slug != $this->curlang->slug)) {
I believe it should fix the issue.