Html code automatically fixed on staging but not on production

I have a website built on Hugo and while implementing new functionality I made a mistake by improperly closing the </code> tag. Strangely, this bug didn't show up in the staging environment and the <code><iframe></code> tag was fixed for users in different browsers and countries (automatically fixed by the browser I think). However, on the production server, the wrong closing tag caused the layout to break. I'm not sure which direction to investigate to get to the root of the problem. I do think this has nothing to do with hugo. </p> <ol> <li> I would be grateful if you could suggest a possible reason why everything is working fine in staging environment instead of production environment? </li> <li>Is there some way to prevent tags from being automatically fixed when staging? </li> </ol></p></div><div class='info mb-10'><a rel="nofollow" href=" http://m.php.cn/member/1271974.html"><img src='https://www.php.cn/static/images/user_avatar.jpg' alt="P粉464113078"><span style="margin-left: 5px;">P粉464113078</span></a><span class='pl-10'>386 days ago</span><span class='pl-10'>1011 <b class="kclbcollectb"></b></span></div></div><div class="course-list discuss layui-clear bg-white"><h3>reply all(1)<span class="detail_answer"><span id="discuss-wenda">I'll reply</span></span></h3><li class="layui-clear"><div class="discuss-img"><img src="https://www.php.cn/static/images/user_avatar.jpg" alt="P粉998920744"></div><div class="info f-left ml-10"><p><a rel="nofollow" href="http://m.php.cn/member/1271518.html" fid="" class="replyer-name">P粉998920744</a><span>2023-09-16 12:07:19</span></p><p class="content Overflow_line"><p>Maybe you tested using a different browser. </p> <p>Validate your HTML using something like <a href="https://validator.w3.org/" rel="nofollow noreferrer">https://validator.w3.org/</a>. </ p></p><span class="detail_answer2" style="float: left" fid="256548"><div class="btn wenda-second-btn" name="P粉998920744" fid="256548">reply</div></span><i class="layui-icon layui-icon-praise wenda-praise-btn"><span>0</span></i></div></li><div class='more'></div></div><div class='discuss-submit bg-white'><li class='info layui-clear'><span class='f-left' id='discuss-submit-close'>Cancel</span><span class='f-left wenda-reply-text'>reply</span></li><li class='layui-clear'><textarea type='text' rows="6" placeholder="Please enter the content for your review" class="wenda-reply-content-text"></textarea></li><li class='layui-clear'><button 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