Today, on an LNER train, there was an issue with someone a couple of seats down trying to display a ticket on a phone. The guard said he would come back after he had finished the coach. When he did, the ticket could still not be displayed. The guard asked if he could use the phone. Permission was given and lengthy tapping was undertaken, at the end of which the guard said that the problem was that the Wifi was not working in that coach (it was - I was using it). By this time the train was approaching the next stop and the guard went to deal with station duties. After departure he returned and, finally, after more tapping, the ticket was displayed for inspection.
All this took upwards of 15 mins and prevented the guard from moving on to check tickets in the next coach. Prior to this kerfuffle the guard had checked and stamped my paper ticket in seconds.