Highlight of first heredoc with quotes broken depending on how many characters exists before it

[flaviovs]

It took me some time to replicate this with a minimal example: when the file below loads, the single quote inside the heredoc is interpreted as an opening string, breaking the highlight from there downwards. Now the strangest things:

• If I remove one single character before the heredoc, the file loads with highlighting working fine.
• If I do any edit anywhere before the heredoc -- either adding or removing characters -- then highlighting is fixed.

Can anyone replicate this? Perhaps a font-lock issue?

<?php

//....................

class Test
{
    public function a12345678()
    {
        //........
        //................................................
        //........................
        //.....................................
        //....................................................
        //....
        //
    }

    public function a123456789012345678901()
    {
        // .................

        // ..............
        // ........
        // .

        echo <<<EOTXT
            I'm here.
            EOTXT;
    }

    public function notHighlighted()
    {
    }
}

Here's how it looks in my computer:

Stock Debian Emacs 28.2, php-mode-20240621.742 from ELPA.