It'd literally be the first that we're aware of.
Didn't Young Hunters end up getting confirmed back at some point? I swear it was confirmed as a rushed development to fill a timeslot. And Tri absolutely had a lot of staff movement while it was being made, with less than satisfactory results given how it got worse as it went in.
Young Hunters was produced quickly, but that doesn't necessarily mean problematic.
And the hold a timeslot I don't believe was ever confirmed, it was more fans looking for an explanation.
But the idea that they used it hold a timeslot, for a show that was in production a decent bit before Hunters ever began, etc.
I mean, I've seen Saint Seiya fans say Hunters was cancelled and that Saint Seiya show was moved forward to keep hold of the timeslot.
It's more likely a case of 'kind of close enough to the rumor', Xros did well enough, and it made sense to keep it going (with various changes) while other shows were simply given more time when they probably 'could' have just gone forward as is.
And the tri. stuff is pretty much nonsense The staff was reasonably solid for a multiyear film/ova production. And of course, we saw what Toei thought of how it performed in financial reports and investor Q&As. They were quite happy. It's part of why Kizuna went into production before tri. was done, and Adventure: went into production before Kizuna was done.
The main relevant staff changes were producer related... Toei added their new staff producer to tri. a few from the end, and he's still around. One producer when tri. was near the end moved from Digimon to running the new Toei division in charge of expanding what they did with Dragon Ball. There were of course, other movements, but nothing abnormal.
'Staff movement' is claimed by fans complaining about nearly any Digimon series. It's said about 02 constantly.
The same fans talking about tri. doing poorly were talking about Kizuna doing poorly, etc.
With how many things some fans claim have failed, in a row, you'd figure the franchise would vanish, instead of us continually getting more and more, it being mentioned in financial reports positively, etc.