[Tomker]

The magnet problem is one we haven't encounter yet (and hopefully will not). We did break a few potentiometers two.

We found that the lock could be freed without taking the whole thing apart by spining the dart shaft counterclockwise while holding the motor shaft in place, but that doesn't prevent it from reoccurring.
We tried a few mechanical fixes within the dart itself which seem to lower the chances for it to lock, but don't solve it completely.
With an added mechanical stop, raising the bottom limit and using code to decelerate the motor when lowering the arm, it doesn't seem to get stuck (we didn't have too much time to test it though).

This product really is great when it functions properly, but given its price and how distructive it might be to itself and the surrounding mechanisms, I feel like there's not enough technical information about how to safely work with it. We are really dependant on using its entire range and are not able to change our design at this point.
Hopefully all problems are behind us and we'll be able to focus on other things.

Btw - either we assembled it incorrectly or the highest position for the hall effects is lower than the dart's higheat point, while the lowest position for them is lower than the dart's lowest point.
At the moment we solely rely on the potentiometer and it seems to work fine