PstgreSQL version is showing 10 as per Drupal 9 requirements , it needs to be updated to 12 or Higher
On inevestigaion found Drupal Core applying those changes to HTML DOM Element, which disrupted the behavior of Left Nav menu in API Doc rendering
There are other Jquery's with similar effect to HTML DOM Element:
web\core\misc\tableheader.es6.js:
this.$html.css(
'scroll-padding-top',
displace.offsets.top +
(this.stickyVisible ? this.$stickyTable.height() : 0),
);
web\core\misc\tableheader.js:
this.$html.css('scroll-padding-top', displace.offsets.top + (this.stickyVisible ? this.$stickyTable.height() : 0));
The Drupal Core Jquery affecting or applying the *scroll-padding-top to HTML DOM element in actual is:*
\web\core\modules\toolbar\js\views\ToolbarVisualView.js
Deleting those configs works
samhaldia → created an issue.