When size is set for the second of two panes only the gutter element has set aria-valuenow to *, which is not a valid value for this attribute and results in accessibility issues.
To reproduce, create this minimal boilerplate:
<as-split>
<as-split-area></as-split-area>
<as-split-area size="30"></as-split-area>
</as-split>
and check the .as-split-gutter element, now with aria-valuenow incorrectly set to *