Safety

The motor or servo gets hot and stops

That is a stall or an overloaded pin. Unplug. Do not hold the shaft to “test torque.”

The problem

A servo hums and warms, a DC motor smells, or the board resets when the wheels catch.

Stall current: The extra electricity a motor draws when it cannot turn. It heats the motor and can reset or damage the board.

1
Unplug USB or the battery as soon as you notice heat or a hot-plastic smell. Let the part cool. Do not keep retrying.
2
Free the mechanism. Cardboard in the gear horn, a wheel against the table, or a drawbridge past its end stop are the usual blocks.
3
Do not power a stalled servo for “just a bit longer.” QA rule: if it has not moved in a few seconds and is humming, cut power.
4
USB from a laptop is enough for one micro servo. Several motors at once may need a separate battery pack with a common GND to the board. If the board resets when motors start, that is a power dip, not a code bug.
5
No unsupervised craft knives, hot glue, or lithium packs. Coin cells are the wrong power source for these motors.

If you walked the steps and the mechanism still does not move, write to us. This is the fallback, not the first stop.