Players are “double dipping” on skill checks

The system we are using is Call of Cthulhu, which focuses heavily on investigation. My players will “line up” to re-do skill checks/rolls when they want to achieve something a certain way. In practice that means that when they’re facing a challenge like opening a certain door, they will try to break it one by one so they all can do a strength roll once. While in that situation it’s not that big of a problem (after all, that’s probably the way they’d do it in real life too), there are situations in which it is worse:

CoC makes heavy use of a skill called “Spot Hidden”, which is used when searching an area, person, etc. A passing check will reward the players with information, finding evidence or at least the absolute knowledge that there is nothing of interest to find there.

This leads to my players’ investigators lining up to search each room one by one, and on our last adventure I made the mistake of granting each of them the roll. This quickly proved to be detrimental to the challenge and atmosphere.

I am not sure how to best approach this, although I already have an idea or two:

  • Talking to my players about better differentiating between player knowledge and character knowledge. The character does not know a roll failed, he simply missed something – thus other characters shouldn’t automatically be inclined to check every spot twice.
  • Penalizing repeat searches. This could be either done implicitly by having the character be busy for some time, or explicitly by making use of the CoC rules for forced rerolls – the second try must be justified with a special effort and will have immediate negative results if failing.
  • Not allowing re-rolls (by other characters), unless it’s a forced reroll.
  • Doing these kind of rolls as the Game Master behind the screen, not letting the players know if the roll succeeded. This can keep the excitement up, and will probably more efficient if the GM sometimes rolls the dice without a skill check actually being made, just to keep the players guessing. But it also feels wrong to make player character skill rolls as the GM.

Answers to this question should adhere to Good Subjective, Bad Subjective – it needs to be something you’ve tried or seen tried. Don’t just toss out “ideas” for me to try, I already have ideas. Explain how the thing you’re proposing worked out for you/whatever you’ve observed in play.