Wa alykum asalam. Here is a copy of an explanation of the three fundamental principles including the principles themselves:
"The pebble must fall into the ‘hole of the jamara’, therefore a person aims for the actual ‘pit or hole’ and not the pillar itself. The pillar was not built to be stoned, rather it is simply to highlight the position where to stone, the actual place of stoning is the ‘pit/hole’.
Based upon that, if the pebble was thrown at the pillar itself and it hit the pillar and bounced out without falling into the pit/hole, it would not count.”
Wa alykum asalam wa rahmatullahi wa barakatu. I’m sorry I cannot give you an answer to that. I think specific situations play a key factor in the answer, so if you can, my advice is to get someone you know who speaks Arabic to contact one of the ulema.
Here are the details: