Well, I would first check the IPs you're using. Many times we think our accounts are completely independent, but we might be using proxies with a pretty bad reputation... Use reliable proxy providers and work with clean IPs, my friend. This is the most important thing.
It's not just about the proxy working and having good speed. For social media platforms, those IP addresses need to have a good reputation.
Imagine you and twenty other people sharing the same proxy or the same IP for that account, logically you're going to end up getting banned.
If all the accounts got blocked practically at the same time, I would definitely suspect the IPs.