I've run into this issue twice in the past week now, once with my 3D printer and once with the DataSleeve.
The problem with the printer: The printhead is equipped with a leveling probe used for bed compensation and homing. When homing, the printer would normally move the head down and then stop when the switch is actuated. Instead, the printer has been ignoring the probe and slamming the print head into the bed. This is caused by EMI. I am currently fixing the problem by holding the cables away from the heating element and extruder motor during the homing cycle but need a real fix.
The problem with the DataSleeve: I need to measure a voltage across a battery that's far away from the microcontroller. Either I place the voltage sensor near the battery and route an analog line, or I route the battery voltage and place the sensor near the MCU. Either way, a voltage which needs to be measured somewhat precisely has to be routed over about a meter of cable.
How do I fix EMI in both scenarios? Tin foil? I could only find 1 spool of shielding cable sleeving on Amazon and it was like $20.
EDIT - If you recommend CAT5 ethernet cables, the answer is no. I have no access that I know of to CAT5 ethernet cables.
Assuming you buy cat 5 cable make sure you DO NOT buy CCA (copper coated aluminium). The clue is in the price: CCA is about 1/3 the price of solid copper.
How much is your 3D printer worth now? How much will it be worth when it works properly?
Cat 5 is NOT shielded. It's tightly-twisted, which is another way of reducing noise pick-up. But, the signals are also digital and low-impedance. I assume you have analog signals?