Two things to remember
(1) The Directors duty is to restore equity
(2) To be as fair as possible to the Injured Party
If a pair misboarded for the first time it is deemed a mistake. So Injured parties get Avg Plus (by the way this may only work out as an avg score depending on scores and numbers of pairs) so both Injured pairs get Avg plus.
e.g. if N/S fouled the board and you can’t play it, you and other pair get the Avg +
If the same N/S continues to mess up the N/S boards then 40% is subtracted from their score. ie if they got 100% on the fouled board now they it will be adjusted to 60% and no adjustment to the E/W they played against.
To follow the letter of the law it is considered That an Avg + is better for both Injured parties, if they played it, it may work out 60/40 so 65% each is an advantage.
The other angle to watch for, is when we play in competitions of mixed grade and experience some players maybe under severe pressure. First time playing in a club Major competition, age, inexperience, grade, first few times playing in an outside competition. All have to be taken in consideration.
The rule of thumb is: Avg + for Injured party.
If the same pair are fouling boards continually they are penalised.
Probably give them two Chances. If it is an individual competition most TD’s
will not penalise the offenders. Some TDs do give a penalty on first offence
if there is a lot of experience in the game and they feel the offenders should
know better.
This all comes under "Directors Duties and Powers" in the Laws of Bridge
What happens if players misboarded deliberate
TD can try deal with that as separate issue and adjust the
Pairs final scores, It is unlikely that many people would stoop this low!!