Hello
Even 12 digits are far to go to solve a 14 digit diff!
How long are you mining on solo? I am about a couple of months already and never went more than 12 digit.
Also i think latency matters!Where are you located?
How many shares have you submitted? My best share is closely matching the number of shares I submitted -> e.g. lets say 1% luck and best share 100 times worse than target difficulty.