Hi there, 5M.
Let's do some troubleshooting steps to see to boost your browsing speed.
You can log in to QuickBooks in a private window to disable the cache from saving your browsing data. If you can upload paychecks faster, you can go back to your regular browser and clear the cache. If it's still the same, you can use a different browser.
By the way, a cache temporarily stores your browsing data, so it reloads quickly when you revisit a page. However, you'll also experience lags when it's full. This is why we tried the private browser first to see how QuickBooks behaves while the cache is locked from saving new data.
Lastly, our phone agents is always ready to help you further if the behavior persists. You can reach them using the steps given by JanyRoseB.
We're just around if you need anything else.