I'm glad you've reached out to the QuickBooks Community. Let me help isolate the problem when entering an owner's draw in QuickBooks Online (QBO).
I've checked our investigation list to verify if there's an on-going issue about the owner's draw transaction in QBO, but we have no reports of any. I also replicated this on my QuickBooks sample file, and it just works fine.
To check if it's browser related, let's perform the basic troubleshooting steps by opening your browser in incognito/private mode. This mode doesn't use the existing cache data files to load a webpage.
Here are the keyboard shortcuts to open a private browser: