Why did validation of lead cards fail in the end of the event?

Version 4.13 (August 2018): A warning is shown when this problem occurs, both in normal events and in Swiss Pairs.

Q: We played a 36-board event today with lead card validation. Boards 33-36 were tough. I believe that Magic Contest used 33-36 while Bridgemate/server used 1-4, so it was difficult to randomly find the right lead card.

A1: The problem is in the board numbering and that Bridgemate does not handle several identical board numbers with different hand records. You solve this by turning off either Restart board numbering after… or Use the hand record to validate the lead. Both options are found in Contest menu > Settings > Bridgemate, the former in the first tab, and the latter in the Bridgemate Control settings tab.

A2: Another solution is to manually upload a new hand record after the first 32 boards. This hand record file should only contain the boards from 33 and up. Since the hand record file will start with 33, which means 1 (*), Bridgemate Control Software (BCS) will interpret this correctly. The upload must be done manually through BCS.

(*) Most hand record files do not contain board numbers. Instead, the first board is considered board 1. This is what you need to upload to BCS.

In Scandinavia, at least in Sweden, Norway and Iceland, it is very popular to play continuous barometer events, say 42 or 57 boards. The boards are not divided into sessions as in the rest of the world.

Often there is a break in the board numbering after 32, restarting on 1 (33). This means the physical board numbers are 1-32/1-10 or 1-32/1-25 while the hand record file contains 1-42 or 1-57. The duplication of board numbers (1-10 twice with different hand layout) is solved by Magic Contest based on the round number.

When lead validation is activated, a conflict arises in BCS. Whereas Magic Contest has no problem with the “duplicate” board numbers 1, Bridgemate has a big problem. The official reply from Bridgemate is the following:

A: ​Uploading a new hand record file is the only thing that will work. BCS and Bridgemate consider the two occurrences of board number 1, once in the first round and later in another round, the same board, as long as they are within the same session. There is no way to go around this. I guess in Magic Contest you can link a board number to a specific round and based on this combination, relabel the board number of the incoming score. There is however nothing like that in the Bridgemate architecture.