The lock box worked without problems for all the guests before Glenn, and works for the cleaners who use the lockbox multiple times a week. The property was just renovated, and the tradespeople had no problem either. The following three guests had no problem using the lockbox to get access. So I can confidently state that guests should have no problem in accessing the apartment using the lockbox.
Glenn arrived many hours after his stated check in time, it was almost midnight. When I spoke to him on the phone to assist, his speech was inexact, aggressive, and blurry. The two photos he took of the lockbox to send me were completely out of focus. Whether he had had a few drinks or there was some other issue I'm not sure. I guess in this condition it could be difficult for someone to follow instructions or have good hand coordination.
From his other reviews, it seems Glenn is often at the centre of disputes with hosts and prone to exaggeration. Glenn says I have "struggled" with the lockbox at this apartment. What I actually said was "I've had similar issues myself (with lockboxes in general) on occasion, the numbers do need to be aligned just so and if they are a tiny bit out it doesn't work." Unfortunately, for whatever reason, Glenn just didn't have the skills required to do this simple task.