堵著 vs 遇著

There seems to be confusion amongst some people between du2 dioh8 堵著 and ngo6 dioh8 遇著. 

In LLL, page 161, you can read du2 堵 as to mean 碰巧遇上  which means to meet or to encounter by chance or concidence.  

碰巧遇上

Then how about ngo6 遇. In the word dictionary, on page 376, it explains ngo6 dioh8 遇著.  In Mandarin, it means yu4dao4 遇到 or peng4dao4 碰到 which means to run into or meet by chance. 

Neither dictionary explain their difference.  I was taught my ZiHong this and I cannot forget the difference

遇著個人 - to meet a person by chance 

堵著個事 - to meet an event by chance 

遇著