I found a work around for one of my cameras (Amcrest 841 PTZ model non version 3) as it will return with a http error 500 code (Internal Server Error) often when you ask for a snapshot. This happens when you ask with any web browser, even at slow refresh rates. Since this camera appears to be made by Dahua, other cameras that share the same firmware code may find this useful.
After applying at least 3 different firmware updates, each time this fault and fix is still needed and works each time…
Set camera to take snapshots at 1 second intervals.
Setup the schedule to always be able to take snapshots, Note there is no green here so only when an alarm goes off the snapshots are set to be taken at 1 second intervals.
This step also needs to be done, you need to supply a destination for the snapshots, I have tried both FTP and NAS boxes ticked and they both work. You can have the nas/ftp disabled on the next TAB page so they don’t get sent, however it only works if you tick a box here.