save the second picture while the first one is still being saved.
</p>
<p>
<span class="fileName">png</span> files can take 10 or more seconds to save on a
Pi 4 because there is no hardware support for them.
You may also see this message if the
<span class="WebUISetting">Delay</span>
between images is too short, e.g., less than a second.
</p>
<p>
There also may be messages like these in <span class="fileName">/var/log/lighttpd/error.log</span>:
<pre>
2021-10-19 15:17:10: (chunk.c.831) file shrunk: /home/pi/