When I first start Thunderbird it works fine, for a while (as in possibly days). Then I notice when I try to send an email it just spins its wheels. When I shit it down then restart I get a poo-up saying Thunderbird is already running but not responding. Checking task manager I see two instances of Thunderbrd.exe in the liist. In order to successfully restart it I must first kill all instances (I use Sysinternals pskill.exe for this). Then when it restarts it typically downloads a messages that were previously blocked. I've seen this behaviour even without firt trying a send. If I am expecting an email that isn't appearing (there is no indication of a problem when I try a demand fetch) I know that I'll have to do the same pskill/restart to fix it. I'm running Thunderbird 115.8.1 (64-bit) on Windows 11 Home (currently up to date).