Browser that doesn't reload tabs all the time
Turns out the OPs issue only occurred in the Chrome browser, and when using Chrome Beta it worked (sort of).



Old Answer:

Try going to chrome://flags

Look for "Auto Reload" tags, turn them off:

chrome://flags/#enable-offline-auto-reload
chrome://flags/#enable-offline-auto-reload-visible-only


Relaunch Chrome (using the button at the bottom after you have toggled the flags)

If the problem persists, it is not because the page is reloading, it is because it is being redrawn, i.e. it is already downloaded, just not displayed to the user yet. This is due to the fact that, for performance reasons, Chrome doesn't draw all tabs simultaneously.