The Collaborative International Dictionary of English v.0.48:

Flaky \Flak"y\, a.
   1. Consisting of flakes or of small, loose masses; lying, or
      cleaving off, in flakes or layers; flakelike.
      [1913 Webster]

            What showers of mortal hail, what flaky fires!
                                                  --Watts.
      [1913 Webster]

            A flaky weight of winter's purest snows.
                                                  --Wordsworth.
      [1913 Webster]

   2. prone to strange or erratic behavior; -- of persons.
      [PJC]

   3. odd, unpredictable or unconventional; offbeat; whacky; --
      of behavior.
      [PJC]

   4. unpredictable, erratic, or unreliable; -- of machinery,
      especially electronic devices. "a flaky computer board."
      [PJC]

WordNet (r) 3.0 (2006):

flaky
    adj 1: made of or resembling flakes; "flaky soap" [syn: flaky,
           flakey]
    2: made of or easily forming flakes [syn: flaky, flakey]
    3: conspicuously or grossly unconventional or unusual;
       "restaurants of bizarre design--one like a hat, another like
       a rabbit"; "famed for his eccentric spelling"; "a freakish
       combination of styles"; "his off-the-wall antics"; "the
       outlandish clothes of teenagers"; "outre and affected stage
       antics" [syn: bizarre, eccentric, freakish, freaky,
       flaky, flakey, gonzo, off-the-wall, outlandish,
       outre]

Moby Thesaurus II by Grady Ward, 1.0:

173 Moby Thesaurus words for "flaky":
   abnormal, anomalous, apish, arbitrary, asinine, asperous, balmy,
   bananas, barmy, bats, batty, beany, befooled, beguiled, besotted,
   bonkers, brainless, branny, buffoonish, buggy, bughouse, bugs,
   capricious, chalklike, chalky, cockeyed, comminute, comminuted,
   crackers, crank, crankish, cranky, crazy, credulous, crotchety,
   crushed, cuckoo, daffy, daft, dazed, detrital, detrited, deviant,
   deviative, different, dippy, disintegrated, divergent, dizzy,
   doting, dotty, dumb, dusty, eccentric, efflorescent, erratic,
   exceptional, fanciful, fantasied, fantastic, farinaceous,
   fatuitous, fatuous, fey, fine, flipped, flocculent, floury, fond,
   fool, foolheaded, foolish, freaked-out, freakish, fruitcakey,
   fruity, fuddled, funny, furfuraceous, futile, gaga, gone to dust,
   goofy, grated, ground, gulled, harebrained, haywire, humorsome,
   idiocratic, idiosyncratic, idiotic, imbecile, impalpable, inane,
   inept, infatuated, insane, irregular, just plain nuts, kinky,
   kooky, lentiginous, lepidote, levigated, loony, loopy, mad,
   maggoty, maudlin, mealy, milled, moody, moronic, motiveless,
   notional, nuts, nutty, odd, oddball, off the hinges, off the track,
   off the wall, peculiar, pestled, petulant, potty, powdered,
   powdery, pulverant, pulverized, pulverulent, queer, quirky,
   reduced to powder, round the bend, sappy, scabby, scabious,
   scabrous, scaly, scobicular, scobiform, screwball, screwballs,
   screwy, scurfy, senseless, sentimental, sharded, shredded, silly,
   singular, slaphappy, squamous, strange, stupid, temperamental,
   thoughtless, triturated, twisted, unconventional, unnatural,
   unreasonable, unrestrained, vagarious, vagrant, wacky, wanton,
   wayward, wet, whimsical, witless



The Jargon File (version 4.4.7, 29 Dec 2003):

flaky
 adj.

    (var sp. flakey) 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.


The Free On-line Dictionary of Computing (30 December 2018):

flaky

   (Or "flakey") 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 favour of finishing what you start are low.
   Commonwealth hackish prefers dodgy.

   [Jargon File]

   (1996-01-05)