Code Blocks breaking pages

Hello, I'm somewhat new to website building/coding so this may be an easy fix and I might be doing something completely wrong. I'm having an issue where code blocks "break" whatever page they are on. This spontaneously happened, and I made no changes to any code blocks or custom CSS between when the pages were functioning correctly and when they broke. The pages with code blocks all open with no header or footer and will remove any blocks on the page, however, the background remains. The code blocks contain code copied directly from our POS system that embeds Iframes in the page.

I have some custom design CSS on my site, but I have tried deleting all custom CSS design coding and deleting the code blocks on the existing broken pages, but nothing returns them to normal. If I remake the pages, the code blocks will function and open the iframes with a functioning header and footer until I save and exit, and then the page will load broken. If I remake the pages exactly the same as they were made previously, however instead of using code blocks, use markdown blocks with the same code from the code blocks, they function 100% normally. 

I also have no code injection and the pages aren't in member areas. I have since replaced most of these pages in my navigation with pages using markdown blocks instead, however, I would like to figure out why the code blocks are doing this or what I am doing wrong.

I would greatly appreciate it if anyone has any insight on why this may be happening because I am completely stumped and ss support will not help with coding issues. Thank you in advance!

broken page:https://www.bouldersgym.com/localdeals 

broken page: https://www.bouldersgym.com/classcalendar3 --> exact duplicate with markdown blocks: https://www.bouldersgym.com/classcalendar

broken page: https://www.bouldersgym.com/signinwaiver3--> exact duplicate with markdownhttps://www.bouldersgym.com/signinwaiver

In case anyone else has this issue, I figured it out. It seems like ss code blocks might have stopped allowing for code to be formatted like how our POS system makes it:

<iframe width="100%" height="100%" src="https://bouldersgym.portal.approach.app/pass-type/55/embed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen />

and wants it like:

<iframe width="100%" height="100%" src="https://bouldersgym.portal.approach.app/pass-type/55/embed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></frame>

for some reason, the first way still works in markdown blocks and only is giving me issues in code blocks, and this has happened somewhat randomly as our code blocks have been formatted the first way unchanged and functioning up until recently. Maybe an update from Squarespace or something?