@MrHM Due to their construction, breadboards can have a lot more “capacitance” themselves than a bare, isolated wire would.
Here are a two resources that may provide some insight:
(Disclaimer: This isn’t an area I know much about…The following is speculation based on the above) The video shows that capacitance added can be 2-25pF (a lot more than a simple wire that’s short/straight/isolated). The added capacitance depends on how the breadboard is used — using two side-by-side columns has higher capacitance than separating them. Longer strips (like the power rails) will have more capacitance than shorter strips (columns). The nRF article shows that the micro:bit will be charging/discharging capacitors to measure touch and detection depends on how long it takes to charge/discharge…I’d expect a large change in the overall amount of capacitance to have a large impact on how (or if) it works.
One suggestion: Try to avoid the use of side-by-side pins on the micro:bit (maybe use every other pin). This would reduce the capacitance added by the breadboard. If you try this, let us know what you find!
P.S. Other resources that may be worth looking at: