Does your Sapphire GPU have that BIOS switch where you can switch to 3 different BIOS versions depending on what you are going to use the GPU for?
If so have you tried a different BIOS version via the BIOS Switch to see if it runs more stable?
Have you tried to Stress test your GPU card to see if it crashes or not? Furmark is a good Stress test for GPUs and I personally like OCCT which also Stress test the PSU. If your GPU card passes all the Stress tests then most likely it is a AMD Driver issue.
In the games it crashes have you tried different Radeon Game Settings or the Game's own Settings to see if it stabilizes?
Otherwise, unless another RX5700 User knows a fix I suggest you open an AMD Service Request (Official AMD Support): https://www.amd.com/en/support/contact-email-form
Truthfully many Users have been having issues with the rx5700 series GPU cards and AMD drivers in the past.