or is it that the character itself is badly coded?
I don't think it's the latter since everything works fine when he/she is on their own.
Badly coded is the correct term. A helper is essentially a complete clone of the character in terms of memory strain on the engine. If a character is constantly hitting the 56 helper limit, then there is a serious optimization problem.
Lack of proper helper optimizations is common, especially with the advent of faster computers. In winmugen days it was enough to spawn / respawn a set of 2 or 3 helpers in quick succession to slow down the engine on Haswell quad cores (which were top of the line computers at the time). If you wanted your character to not lag the engine, you had to get creative about optimizing the effects you were trying to produce.
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