I've been having the same issue. Making incremental progress but I'm still getting forced restarts at a particular scene in the Shadowbringers quest.

So I used to have this same issue whenever viewing the Leviathan cutscene and having the Framerate capped at 60fps by the in-game setting. I then figured out that if I changed it to uncapped, I would no longer force to restart when viewing that scene. So I thought I had fixed the problem, oh but lo and behold, in Shadowbringers they decided to initiate a cap of 90fps when select the uncapped option. Why? No clue, but I'm sure they have their reasons.

Anyways, I've been playing just swimmingly since that day, until I reached the Dungeon Don Mheg. That's where I had my first crash to restart since I had "fixed" the issue. I would crash when the voices in the water would say, "One of us!". Well, I ended up switching to my laptop and, even though it's a weaker system, it was able to run it fine.

Back to the Desktop. Again, everything is going well but I started to notice that the game would only force to restart when I was watching a cutscene with a lot of explosive or particle effects. This was true for the Leviathan cutscene as he would jump out of the water and spray a light mist all over the screen. Then in the Don Mheg cutscene where water bubbles would start to pop. It also cut out on me in the opening to the Neverreap boss where there's a tremendous wind effect. Also When facing Lahabrea and Igeyorhm in The Aethereochemical Research Facility right as they would combine themselves and a giant purple / pink lightning like explosion would occur.

Made it all the way through Stormblood without a hitch but the issue reared it's ugly head, as I said earlier, in Don Mheg. Then the quest "View from Above" when the machines explode on the Sin Eaters. Then again after the innocence fight and the mysterious character reveals himself as his hood is blown back by a blast of light. Then there are multiple parts in the quest "Shadowbringers" that have been consistently crashing me, but I've been able to get passed a few of them.

First it was in the Shadowbringers Cutscene #2 as soon as the protagonist starts coughing up light and turning into a Sin Eater. Again, blasting effects seem to be a theme here. Then later in that quest there's another trip as the final boss gets some Auricite lodged into it's body and the Auricite shards begin to grow. Sometimes I could make it passed that scene and into a part where the entire seen goes dark. Then it would crash when it went dark.

I made slow incremental progress by adjusting certain settings in game and forcing certain settings outside of the game through the Nvidia Display Settings menu. The biggest improvement I have found is by force enabling V-sync and either setting it to "On" or "Adaptive (Half Refresh Rate)" and bouncing between Full Screen and Borderless Widowed. Unfortunately no permanent fix has been found or offered besides playing the game at an unplayable 30fps, which shouldn't be an option as My computer has ample head room to spare GPU and CPU wise depending on the settings (which is another odd thing in and of itself, I'll explain later). Oddly enough I get massive fps boosts when I play uncapped. Far more than my monitor can even handle really. Like 200fps in the inn room ro some crazy number like that. I then notice that my GPU was at 100% utilization. Literally 100%, not almost 100%, exactly 100%. This is in Borderless Windowed Mode and no capped framerate. So I kept the framerate uncapped, set my Nvidia Control Panel refresh rate to 59fps, then chose the "Adaptive (half refresh rate)". This more than halved my GPU utilization down to 30%, oddly still looked smooth for some reason. It seems as though the game with and uncapped framerate was still trying to run at 200+ fps but the Nvidia control panel "Adaptive" setting was forcing it down to 120fps or so. So far so good right? No longer maxing out the GPU, and I should have plenty of headroom for anything the game might throw at me? Wrong. My game would still crash at the same Auricite scene on the final boss. Despite having ample resources to produce a beautiful image at 59fps 1080p (at least by my standards anyways).

So it doesn't work uncapped, and it doesn't work capped, and it doesn't worked uncapped but halved. Changing any other settings has little to no effect on the fps. The only way I can make it through those cutscenes is if I lower my resolution in game to 1080p 24fps, Full Screen, which is an absolute unplayable mess.

I'm far from the only one having this problem as it seems under or over utilization of the GPU has been rampant in one form or another since patch 4.2 but still no word on a fix, just a thread with a collection of data.

Here's hoping we can get something figured out soon. Hoping some of my explanation might help you with tweaking things on your end and possibly shed some light on the issue. A lot of folks have been complaining about a 100% utilization of their Nvidia graphics cards, even beast cards like 2080's and Titan V's. Others have had the opposite problem, with an oddly under utilization of their cards and CPU but the game lags and chugs even though the game could utilize more resources.