Let’s give this a try setup an external bootable drive (something you can use for awhile) Ideally a thunderbolt drive like: [https://www.samsung.com/semiconductor/global.semi.static/PSSD_X5_Brochure_180822.pdf|Samsung X5].
Now we need to make it the boot drive go into your preferences > Startup Disk. Now restart your system with the external connected it should now be the first listed drive on your desktop.
Migrate your apps & stuff over and use your system this way for a week or so. Is it stable or still failing? Let us know!