This is a sort-of follow-up to: Flagging automatically flagged posts as invalid
The difference is that in this case, it is not an automatic flag.
I marked as "invalid" the flags on this answer. However, the flag history says:
disputed - flags should not be used to indicate technical inaccuracies, or an altogether wrong answer
The explanatory text shows that moderator agreed with me that flags on that post are invalid, yet my flag is "disputed". Since I don't have many flags, I was able to find all my disputed flags, and this is really one of them (it really counts as "disputed" like that my action was wrong).
I'm not after any statistics about flags, I just want to find the reasons for this, and to see whether my actions were correct. And if they were, I believe it is a bug in the system.
Remark: I have couple flags of this type (marking other flag as "invalid") that are "helpful". This means that it is not a general case of all "invalid" flags, but rather some (randomly) appearing effect.