Yes, and the reasons are more mundane than the forum threads suggest. Here they are ranked by how often they actually cause a problem, so you can spend your attention on the first one rather than the last.
1. Violating a rule your firm published
This is almost all of it. Not detection, not sophistication — someone did a thing their firm's rules prohibit, usually without having read the rule.
The most common version is copying into accounts you don't own, at a firm that permits copying across your own. The second most common is running automation at a firm that requires authorization for it, having read only the copying rule.
Mitigation: read both rules, keep a dated copy, and ask in writing when the wording is unclear.
2. Breaching a risk rule faster than you would by hand
A copier doesn't break rules on its own, but it does multiply the consequences of one bad decision. Daily loss limits, trailing drawdown and maximum position size all arrive faster across a group than on one account.
This is the one that costs people accounts without any rule about copying being involved at all.
Mitigation: size the group to what your worst day can survive, not your best.
3. Consistency rules
Many firms have rules meant to catch a single outsized day carrying an otherwise unremarkable account. These aren't aimed at copiers, but identical trades across accounts can produce the concentration pattern they're written to catch.
Mitigation: read the consistency rule specifically. It's usually separate from everything else.
4. Hedging across accounts
Several firms prohibit holding opposite positions across accounts or in correlated instruments. Straightforward copying doesn't create this — every account gets the same direction — but mixing a copied strategy with discretionary trades on an account in the group can.
Mitigation: know what else is trading on the accounts in your group.
What happens when a firm acts
Outcomes vary by firm and by severity: a warning, a denied payout, closure of the offending account, or closure of every account you hold there. Denied payout is the one that hurts most, because it usually arrives after you've done the hard part.
The thing worth internalizing
Nearly every account lost to this was lost to a rule the trader could have read in five minutes. The tooling is rarely the problem. Reading the rules is cheaper than any of the above and it's the only mitigation that addresses all four.
This is a reference, not advice, and it is not a statement about any firm's rules.