flaky

Etymology

From flake + -y.

adj

1. Consisting of flakes">flakes or of small, loose masses; lying, or cleaving off, in flakes">flakes or layers; flakelike.
2. (informal, of a person) Unreliable; likely to make plans with others but then abandon those plans.
   I have noticed that when hustlers upgrade themselves to models (as distinguished from models who have never hustled) they tend to continue being flaky about appointments. On my last trip to San Juan, Puerto Rico, I was stood up twice. 2014, Joseph Itiel, A Consumer's Guide to Male Hustlers
3. (informal, of a thing) Unreliable; working only on an intermittent basis; likely due to malfunction.
   I cannot enjoy the online game because of my flaky Internet connection.
   Toeava went over unopposed to stretch his side's lead but Japan got on the scoreboard on 56 minutes, wing Hirotoki Onozawa intercepting an attempted offload from Slade, who had a rather flaky game, and running in from the All Blacks' 10m line. September 16, 2011, Ben Dirs, “Rugby World Cup 2011: New Zealand 83-7 Japan”, in BBC Sport