It depends on how you look at it. Brave is routinely flagging (suspending) accounts from people who are violating Terms. Since they delay notices that accounts are flagged, people often don’t find out until they don’t receive their payment. So in that way, yes, it can be common in the grand scheme of things.
In addition, there can be issues with the system that causes delays in payments. There have been times that payments got stuck in a pending state and had to be reactivated to be sent out. You’ll likely see at least one person each month experience an issue like this. Brave has been working on improving systems and it’s much better than it used to be.
Does it happen very often to specific people? Not really. There are some who have very bad luck, such as @lowner who dealt with constantly getting flagged for quite some time (I forget if months or more than a year) before Brave finally was able to get it resolved and pretty much assured them they won’t have any issues again in the future.