Yes this happens to me as I was also reading ad making notes for a medical book and I lot everything. It didn’t backup or keep any of the notes I’d made over about 7 days of reading.Excellent! Glad I could help
Has any one had any issues with the Kindle insights? I had a reading streak and it didn’t record Feb 14 and 15 and said the last data had been received 13 Feb, it’s now updated to 16 Feb and is back to 1 day I wonder why it didn’t capture 14/15 Feb and if there is anything I can do about it?