99% of views coming from subscribers, down 65,000 watch hours per day in the last 3 months, wtf is happening?

Big channel. The page was getting 50-70k watch hours PER DAY over the whole year. Overnight, literally one night - not 2 uploads, nothing gradual... I wish I could post a screenshot here.

CTR, AVD has been the highest its been all year.

The amount of subscribers watching the videos have doubled. 99% of views are coming from subscribers. Not 92%, or 82%, 99%. These are long form videos.. The shorts tanked too going from a few million per post to 1k.

99% subscriber viewership seems so ridiculously wild, that it doesn't scream to me "Your content is shit. Do better." It's an established channel with an established format. I've seen many channels die organically, and this is a complete outlier from that.

Anyone have any experience on this or perspective?