We deal with the Sales Manager but suspect the CEO is behind these problems. Replacing this supplier is impossible because they have a unique product our clients demand. How to communicate our dissatisfaction and need for urgency without fracturing or hurting the relationship? FYI they're in a developing country that differs from typical Western standards and behaviors.
I think this question belongs to the same issue as I replied in this link. Please check and let me know if you have any further questions. We can discuss over a call, I am happy to help.