The algorithm is flaky. It seems like it ought to work, except that in many weird situations (which you might not fully understand), it gives unwanted results.
Per the Jargon File:
Subject to frequent lossage. This use is of course related to the common slang use of the word to describe a person as eccentric, crazy, or just unreliable. A system that is flaky is working, sort of — enough that you are tempted to try to use it — but fails frequently enough that the odds in favor of finishing what you start are low. Commonwealth hackish prefers dodgy or wonky.
In other words, the algorithm frequently produces buggy output.