Scheduled sales are not required, only recommended. If an unscheduled sale is made, there might be insider trading issues, and might trigger an investigation. That said, it would be easy to argue the sale was due to public information, i.e. the stock going up 100x in 6 months.

See Rule 10b5-1

I mean, they have to be scheduled in advance to avoid even the implication of trading based on non-public information.

I would find it hard to believe an accusation of "insider trading" if an GameStop officer sold a bunch of stock last week, rather than the much more likely public-information explanation of "we're definitely not a $25B company and everyone knows it".