I reviewed our system, and we haven't received any related reports to your concern.
QuickBooks Online and your browser use cache to accelerate background processes. However, too much of it can also cause unexpected or unusual behaviors while using the program. We can do browser troubleshooting steps to get rid of any cache-related issues.
Access your account using a private browser. It uses but doesn't store cache. Then, create the invoices again.
If you can add the service items successfully, we can clear the cache of your regular browser.