Usual failures revolve around inconsistant adjustments, settings of, or even the entire illumination not working and needing to be whacked to turn back on, cheap switches that break, non waterproofed, poor opticla quality, excessive dark tint for dots, general unreliability, battery life, etc.
For 2nd focal plane vaiables you get POI shift with shifting magnification, for magnified optics in general crap inside the optics like dark spots, and of course lts of the thing s listed in paragraph one.
If none of that bothers you a cheap optic is right up your alley. For example... remember not to use setting 5 becasue its broken, if it flickers whack it, the on/off switch is broken so use the brightness adjustment turned to minimum to increase battery life when optic should be off, or not minding some of the LEDs that make up your reticle have died from less than .223 recoil and so on... I have experienced all these.
Have fun.
To be honest losing zero if you dont do any adjusting is the rareest of all cheap optic problems but it does happen... I have never seen it.