When I try to print something I keep getting a "format error" from the printer on a line containing "{travel_speed}"

cura
slicer-specific

#1

If you see something like this in the terminal tab, possibly in form of an endless loop:

Send: N18 G1 F{travel_speed}*81
Recv: Error:Format error
Recv:
Recv: Resend:18

you are using Cura and are using {travel_speed} instead of {speed_travel} as a placeholder for the travel speed in your start/stop GCODE scripts in Cura.

Older versions of Cura used to use the former, then some versions later this was changed to the latter and since then people copying code meant for older versions into newer ones have been running into this issue and it doesn't seem to die.

Just replace all occurrences of {travel_speed} with {speed_travel} and reslice your files.