503 Service Temporarily Unavailable - server: cloudlfare

I don’t know why but Cloudflare return 503 error for some users.
My website has been banned from bing because website scan return 503 error.
I’ve made homepage page rule cache everything still - nothing help.

Also It adds in bottom some malicious script

<script>(function(){var js = "window['__CF$cv$params']={r:'7335cd748cbb248b',m:'Lbnt.tjYMasIHJrNztzMaIuX2FGEZUloqBkHwzjVNCM-1659264935-0-AXYAxyKejK3L5lYsD0nXgcpXr5ygF+kbV8TU1UHkXxbT3JmDA3eqYSAjeUZGUBDQdi/mvoX8fGLjnl6jQKR7mQvRRmcXvMKqOsH10BwVZ1tBl3tgrSQviecxcfZHLUw+uw==',s:[0x65dc3fa8bc,0x2e1349e97e],u:'/cdn-cgi/challenge-platform/h/g'};var now=Date.now()/1000,offset=14400,ts=''+(Math.floor(now)-Math.floor(now%offset)),_cpo=document.createElement('script');_cpo.nonce='',_cpo.src='/cdn-cgi/challenge-platform/h/g/scripts/alpha/invisible.js?ts='+ts,document.getElementsByTagName('head')[0].appendChild(_cpo);";var _0xh = document.createElement('iframe');_0xh.height = 1;_0xh.width = 1;_0xh.style.position = 'absolute';_0xh.style.top = 0;_0xh.style.left = 0;_0xh.style.border = 'none';_0xh.style.visibility = 'hidden';document.body.appendChild(_0xh);function handler() {var _0xi = _0xh.contentDocument || _0xh.contentWindow.document;if (_0xi) {var _0xj = _0xi.createElement('script');_0xj.nonce = '';_0xj.innerHTML = js;_0xi.getElementsByTagName('head')[0].appendChild(_0xj);}}if (document.readyState !== 'loading') {handler();} else if (window.addEventListener) {document.addEventListener('DOMContentLoaded', handler);} else {var prev = document.onreadystatechange || function () {};document.onreadystatechange = function (e) {prev(e);if (document.readyState !== 'loading') {document.onreadystatechange = prev;handler();}};}})();</script></body>
</html>

I have turned off security and turned off Browser Integrity Check - still the same malicious code is added to homepage.
Problem is that not everyone gets 503, but bing and this website _smallseotools.com/get-http-headers/ return 503 on checking _steamid.xyz