This is almost certainly due to problems with the USB connection or the power supply to the camera or computer:
- USB cable: Excessively long, damaged or loose USB cables can cause problems. If possible use the USB cable that came with the camera and plug it in directly to a USB port on the computer. Ensure the cable is not damaged and is firmly connected at both ends. Don't use inexpensive low-quality cables.
- USB hubs: These can cause problems particularly if they are self-powered. If you do need to use a USB hub it will probably be more reliable if it is externally powered.
- Too Many Hub Connections: Some hubs are limited in the amount of data they can handle. Don't put too many devices on one hub. If you get a Download Image error, don't connect the camera and a TB3 or other Moco device through the same hub.
- Active USB cables: These are actually a USB cable with a self-powered single port USB hub on the end (see USB hubs above).
- Computer power supply problems: Some laptops don't have enough power to run the USB ports properly when running from batteries. Usually running the laptop from an AC adapter will fix the problem. Some desktop computers have additional USB ports which don't receive as much power as the main USB ports. If you are having reliability problems it is worth trying different USB ports on the computer.
- Camera power supply problems: Some cameras may become unreliable as their batteries begin to run down. This is more likely to be a problem when using live view as this uses more power than normal camera operation.
- Voltage spikes from other equipment: Using a good quality surge protector should reduce the risk of this.