I think substances and/or unbalanced people are the culprits here. A new guideline for you before you will agree to attend an event or go away on an overnight trip with someone is you need to have observed them enough to know definitely whether there is the tendency to overindulge in substances OR become angry/behave in an unbalanced way. You do not have to only have friends who don't use. You just need friends who use MODERATELY and are not negatively influenced by substances or become unbalanced in particular situations.

I think starting out as friends doing time-limited activities locally for a few hours is good, and then gradually lengthen the time of the activities as time goes on so you can see how the person is in different environments. This might mean that you don't go to a long-distance event or on a fun trip for 6 months or longer, but this would be like any other relationship (including romantic) - you need solid proof that this person has their head about them before you will agree to a lengthy amount of time with people.