I did an industrial automation class in college. We had a PLC setup with optical sensors and were sorting cylinders by height. We wired it up tested it, then c

I did an industrial automation class in college. We had a PLC setup with optical sensors and were sorting cylinders by height. We wired it up tested it, then called the TA over to review. It failed despite no changes and working minutes earlier. We changed some logic, tested again, and again called the TA over. It failed. We had another team look at our code and see if we were missing something obvious. Nope, it looked the same. Finally I realized I was standing when we did the testing. I shaded the sensors and kept them from being overloaded with sunlight. We were the only table in direct sunlight, so only we were experiencing the issue.