image from the awesome Flowalistik

My Z axis won't home, it crashes into the bed (or endstop) ¶ 

Read Configuring RepRapFirmware for a Cartesian printer: Homing Z

I can control fans 0 and 2, but not fan 1 ¶ 

Fan 1 output is configured in thermostatic mode by default and also turns on automatically when the processor is started up or reset. This is for added safety when you use it to control the hot end fan. See Connecting and configuring fans: Thermostatically controlled fansand also the following section on that page.

I upgraded from firmware 1.18.2 or earlier to firmware 1.19 or later, and now when I try to probe the bed using G32, G29 or G30, it makes unexpected movements ¶ 

Delete the deployprobe.g and retractprobe.g files in the /sys folder of the SD card, unless you have set them up specifically to handle a type of Z probe that needs to be deployed (e.g. BLTouch).

When my print finishes, it retracts all the filament out of the printer ¶ 

You have configured your slicer to use absolute extrusion coordinates, then you have used a relative extrusion command in your slicer end gcode script to retract a little filament, without switching to relative extrusion mode first.

• We recommend you set your slicer to generate relative extruder coordinates. Include the M83 command in your start gcode.
• If your slicer doesn't support generating relative extrusion coordinates, place either a M83 command or a G92 E0 command before the G1 E-xxx in your end gcode that you want to retract a little filament.

When I try to home my printer, sometimes the carriage or carriages move only part of the way towards the homing switches, and I have to command it to home again to make it go all the way ¶ 

If your printer is a delta, open the homedelta.g file in the System Editor of the web interface. Look for the first G1 S1 line in that file. The X, Y and Z parameters on that line are the maximum distances that the carriages will move up when homing. Increase them to be a little larger than the maximum distance that the carriages can ever be below the homing switches.

If your printer is a Cartesian, CoreXY etc. the solution is similar. For example, if the X axis sometimes fails to home all the way, look for the first G1 S1 X command in homex.g and increase the X parameter to at least the length of the axis. Do the same in homeall.g.

Some Features of Duet Web Control not working ¶ 

This is often caused by using an incompatible browser. Chrome and Firefox browsers fully supports DuetWebControl however Edge and IE have problems. (https://www.duet3d.com/forum/thread.php?...).

DWC file editor works in Safari 10.0.1 and later. (Won't work in any earlier versions), from the thread linked above.

If this is not the case ensure you are running the llatest stable versions of the firmware and Duet Web Control

What to do if your Duet won't respond ¶ 

The the What to do if your Duet won't respond page