Proxy switcher sometimes doesn't work while the current proxy is unavailable and all the other proxies in the list are available and user can manually test all of them.
After spending the specified time to switch, it won't switch.
Even after waiting for an hour, it won't switch.
But other proxies in the list are all available and can be tested manually at any time.
I have tested this problem many times with a list which I have made as a test case.
I'm not sure what's the steps to reproduce it.
Having an unavailable proxy and many available proxies:
all versions since adding proxy rotation