Like many of you, I've been in Quicken for 25+ years. I have dealt with double transaction/missing transaction/failed one-step update issues at least a half dozen times. I keep an hourly snapshot backup on a network RAID and have had to revert to an earlier file at least twice. I have both onsite and offsite backups of the files (I run multiple files, one for each of several entities).
My emergency strategy should a revert fail permanently, is to start a new file as some of you have done. So far though reverting has always forestalled this, although I've had to re-enter data.
I've found Quicken support to be adequate if not excellent.
I wish the program itself was better, but won't move unless forced, or until a clear nirvana alternative becomes obvious.
Why do people keep 30 years of data, BTW? How do you use it?
Two main ways.
1. I can answer questions like "when did we replace the furnace", "How much did we give XXX for her graduation", "When did we go to YYY" etc, without digging through files in the basement. It's an invaluable financial fossil record.
2. I can answer questions about spending. Before retiring last year, I worked up a spreadsheet of our last 6-7 years of spending by major category, and worked out what our spending would be in retirement. As it turned out, I was on target for 2021 spending, despite Covid and retirement changes. It takes me a half day each year to add to this spreadsheet using Quicken reporting data, and it gives me a good summary I can share with my spouse, use to jog my memory, etc.
Despite very little trading on my part, I find my balances in investment accounts don't quite track reality. They're close enough that I feel I can rely on the net worth number Quicken comes up with though, and that's good enough for me. Quicken is primarily about spending for me, and secondarily about that only-accurate-to-within-a-few-percent net worth number.