The theatre coat check

Text: an original contemporary report-style practice extract.

The theatre replaced handwritten coat-check tickets with numbered pairs after several numbers became difficult to read in the dim foyer. One matching ticket stayed with the coat and the other went to its owner. The new tickets did not include names. Staff still asked visitors to remove valuables from pockets before handing over a coat. After the first performance, the manager counted the unused pairs to check how many had been issued. The queue moved slowly, but nobody had to decipher a smudged number.

From the extract, identify one problem that led to the ticket change.