capture_jpeg() fully crashes the Pi

This will be fixed when we implement #429 (closed)

On v3, capturing and saving an image with

x = cam.capture_jpeg(resolution = "full")
x.save('1.jpeg')

Normally takes around 0.3 seconds to encode. On the 5th capture of a scan, instead took 9 seconds to encode, followed by the Raspberry Pi itself crashing. No ability to restart server, ssh, etc. Required full power cycle

See related: #293 (closed) #319