HasanMerkit Hm, interesting. I cannot reproduce the issue posting the same link but I can see that there is some issue with the code that the post body forms...
<iframe
data-s9e-mediaembed="twitter" allow="autoplay *" allowfullscreen=""
loading="lazy"
onload="var c=new MessageChannel;c.port1.onmessage=function(e){style.height=e.data+'px'};contentWindow.postMessage('s9e:init','https://s9e.github.io',[c.port2])"
scrolling="no" all?q="1503033974473760768"" class="hasht"
title="Find posts related to this hashtag"
src="https://s9e.github.io/iframe/2/twitter.min.html <a href=">#1503033974473760768</a>"
style="border:0;height:250px;max-width:550px;width:100%">
</iframe>
Not sure what has happened there. Does the issue remain even if you edit the post?