Without seeing the Notice of Race or Sailing Instructions it is not possible to respond definitely to what they were doing, but I suspect Appendix P rather than fleet umpiring. You can find the Rule 42 interpretations at https://www.sailing.org/our-sport/race-officals/international-judge/international-judges-resources/. World Sailing revamped their website and all former links are now useless. If your NoR / SI indicated that Appendix P applied, then the judges will have been on the water penalizing Rule 42 infractions. If you are a US sailor, best to purchase the US version of the rule book as it includes the US prescriptions. 

The guidelines are not rules.  The rules are what is written in the rule book.  Many classes have examples, both written and video, of what legal and illegal kinetics is considered to look like in their specific boat type to help judges and competitors alike and provide some consistency between events.  But these are not rules.  As far as I know there are no 'prescribed positions' for judging rule 42  The judges position themselves to get the best overall coverage of the fleet that they can.  A judge can make a call from any position provided they are sure that the rule has been broken.

You can find ILCA R42 interpretations at https://www.sailing.org/tools/documents/Rule42Laser201320032014-[16804].pdf

Is there anything we can do about the broken links on World Sailing? The ENTIRETY of appendixes K and L is a broken link at the moment. With enough digging, this info can still be found, but it's not easy.

I am afraid that the only choice is to explore the new website and find the new links. World sailing is aware that many documents, that include links, need to be corrected (example : the different race officials manuals). Some of them are already being updated.

John, thanks for your comments. There actually ARE recommended (though admittedly not mandatory) positions listed in the Rule 42 umpire guide at https://www.sailing.org/tools/documents/Rule42Laser201320032014-[16804].pdf:

Upwind:
Page 2, section 1
"For these breaches to be properly observed and identified the judges must position themselves behind the boat, to be able to connect the body movements with the flicks on the leach.... Both prohibited actions are clearly observable from astern."

Downwind (body pumping and sheet pumping):
Page 3, section 1
"On a reach body pumping may best be seen from behind and to leeward of the Laser, in order to observe the athwartships body movement and the effect it has on the leach. On a run sheet pumping best seen from a position abeam of the observed boat, and to leeward."

Downwind (rocking):
Page 4, section 2
" The best position for judges to observe both the effect of body movement on the boat and any steering by the sailor is from directly astern."

There definitely are better vantage points compared to others for a given boat but when you are trying to watch over 10-15 boats spread out over a section of the course the judges have to do the best they can.  They can't be in the best position for every boat all the time.  But just because they are not in the ideal position doesn't mean they shouldn't make the call if they are sure the rule was broken.  The alternative is either one judge boat for every competitor or no judges at all, and I am sure that's not what we want.