This could just as easily be called the propagation of uncertainty or the propagation of doubt.

(Don’t judge me, Wikipedia is fast and reasonably reliable)
In statistics, propagation of uncertainty (or propagation of error) is the effect of variables’ uncertainties (or errors) on the uncertainty of a function based on them. When the variables are the values of experimental measurements they have uncertainties due to measurement limitations (e.g. instrument precision) which propagate to the combination of variables in the function.

Alright, so most multi-step solution proposals to K4 or Kryptos proper involve sequential manipulations of text/symbols.  Consider the idea that an error at any step is carried along through each series of steps.  It seems logical but consider that for many of the more subjective methods there is a certain amount of variability, a degree of sort of arbitrarily picking “the most likely” or “the obvious” instead of the certain or constrained.  This variability only increases the uncertainty of the final conclusion of the proposal.  Some folks assign more credibility than is due to applying certain clues or steps, you know who you are, at the end of the day it’s still just your opinion.

Keep with me, it’s worth it.

Consider something easier to visualize.  I want you to line up 5 rocks of different colors, how many orientations are possible?
5x4x3x2x1 = 120.  Easy.

Now consider a modest multi-step proposal with 5 steps to an incomplete solution (because why would we still be debating this if someone had solved it?).  Let’s narrow our example even more, at each step the solver has to decide between two choices.  I think we can all agree that if it was this easy, it would have been solved long ago.  Trick question: how likely is it that someone using this small-scale method has even the right possible orientation out of his highly constrained possibilities?
2x2x2x2x2 = 32.

Now 32 doesn’t seem too bad but consider that our solver has likely picked one of those sequences that he prefers.  The arguments he will present for his choice range from “here is a highly detailed, logical analysis leading to my decision” to “I had to pick one so I did”.  In reality, if there’s a point where it’s a literal choice then you have a degree of variability or uncertainty present in your proposed method.  I have yet to take into account the fact that in many multi-step proposals, it’s just as likely to believe some steps are interchangeable.  Just because you kept hitting dead ends and then would read a Morse code phrase which then led to the next brilliant (unsuccessful) step, this doesn’t imply that the sequence of manipulation was meant to follow the sequence of your discoveries or revelations.

If we take our simple method from above and say that each step is interchangeable despite the protests of the author, then how many orientations are possible?
5x4x3x2x1x2x2x2x2x2 = 3,840.

That’s 3,840 possible sequences available in a proposed method (which doesn’t work) with only 5 steps, with only 2 possible options at each step.

Anyone would be willing to argue that not all of those are believable, even I would probably argue for removing some of the possible sequences from consideration.  The problem is that you have to consider each of the 3,840 possible arrangements as equally likely from the start.  Then you have to weed through the possible sequences to remove the most unlikely.  It’s unlikely that you or anyone would have the time and dedication to eliminate every option to find the one true arrangement.  It also doesn’t work to arbitrarily pick one and try and claim that it’s the only one that works.

Okay, let’s scale things back and forth a little.  Not every step of a method will have an option.  Sometimes simply because of the cues the author is following, there is only one possible way of misunderstanding the clues left for us in Kryptos.  Not every step is interchangeable because sometimes as creative as the author was in developing their methods, there are some steps that implicitly rely on a previous step coming first.  Many times these methods will however have more than 5 steps and sometimes quite a few more than 2 possible options to choose from.  We won’t always end up with a couple thousand possible arrangements, sometimes it will be more and sometimes it will be less but it will always be more than 1.  There will always be a degree of uncertainty in the decisions made or in the alignment of the sequences followed.

So far we’ve been discussing uncertainties and variabilities.  The error creeps in sometimes, of varying degrees of probabilities.

There is the error of choosing the wrong method.
There is the error of including an incorrect step in the method.
There is the error of making the wrong choice at a step in the method.
There is the error in completing a step of the method (typos, lining things up wrong, etc.)
There is the error in calculations.

I hope you can see from the discussion that it’s not so much a guarantee that someone will screw up their own method or make a dumb mistake although that is a very real possibility and requires us to check the accuracy of each step.  The guarantee is that there will be a degree of uncertainty that increases as the complexity of the method increases.  Don’t fall into the trap of saying, “well, it just seems so likely” or “when I thought I was stuck, I went back and found this little tidbit that kept me going”.  Some would argue that there is a certain amount of art and interpretation inherent in Kryptos.  I would say that I agree but I think it is in the end.  I have no support for this statement but I would be willing to bet some money that K4 is a tough cryptological challenge, not artsy-fartsy.  The final message of Kryptos is probably very subjective, very philosophical and very easily misunderstood.  We have no real reason to bring flights of fancy into attempts to solve K4.  Keep it grounded and try and find logical support and arguments for everything that you do.  Work to eliminate the variable nature and try and keep the possible rearrangements of your method as low as possible.  Where needed, try and examine multiple possible sequences of your method.

You dramatically increase the odds that you will fail if you don’t work to eliminate doubt, uncertainty, and the potential for error.