We haven't received any reported cases from other users similar to what you encounter while reconciling an account. I've also tested it on my test account, and I was able to perform the process without any error.
As an initial troubleshooting step, please log into your QuickBooks Online (QBO) account using a private browser (incognito). There are times that the browser is full of frequently accessed page resources, causing some unusual behavior.
Here are the keyboard shortcut keys depending on the browser you're using:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox or Internet Explorer).
Control + Option + P (Safari).
If it works, switch back to your current browser and perform a clear cache. Every so often the cache becomes overwhelmed with older data which can potentially cause viewing and performance issues.
Clearing it will refresh the system, and you'll be able to work in a clean slate. However, if the issue persists, try using other supported browsers.
Please know the Community has your back. If you have additional questions, click the Reply button and post a comment. I’m here ready to assist further. Enjoy the rest of the day.