I was shared this problem about 5 years ago, which combines the Cheryl's Birthday problem with the trolley problem:
Spoilers below for my solution!
The Correct Pad
We can first identify how we can stop Cheryl, and later decide whether we want to stop her or not.
Albert says that not only does he not know which blue pad is correct, he knows that Bernard doesn't know. Thus, all pads on Albert's letter must be in columns where there is another pad. Otherwise, Albert couldn't have been sure that Bernard doesn't know. This eliminates letters A and B.
To elaborate, if Albert had gotten the letter A, then there's the possibility that the correct pad is A6. Then Bernard would have gotten the number 6, and he would know which pad is correct. Similarly, if Albert had gotten the letter B, then Bernard would know if the correct pad is B5. So the only way that Albert can be sure that Bernard doesn't know is if Albert had gotten the letter C or D.
Next, Bernard says that he did not know originally, but now he knows. Albert's declaration reduced the possible pads to C1, C3, D1, D2 and D4. Thus, the correct pad must be C3, D2, or D4. If the correct pad was along number 1 (C1 or D1), Bernard still wouldn't know.
Finally, Albert says that now he knows. Thus, the correct pad must be C3, because if Albert had gotten the letter D, he still wouldn't know whether it was D2 or D4.
Crashing the Trolley
Given the choice between actively taking a role in 20 deaths and letting 50 people die due to inaction, my moral compass says to crash them on the correct pad. But difficult situations can lead to freezing up and abdication of responsibility, so it's hard to say what I would actually do.