This line:

causes a currently in session webServer send to stop. Before I make an MCVE, can anyone share why this stopAll exists?

If, while the web server is sending a chunked response, a WiFi event occurs, the chunked response is abandoned and the web browser gives an error. Commenting it out appears to fix the problem but maybe there was a reason for it and something else would be broken after removing it?

It may also have some bearing on an older issue:#1554