How to return the permission missing from the list?

Question

ASUS

Windows 7 x64, GTX 1080 GIGABYTE G1 Gaming, DELL U2417H primary monitor (connected via DP), second ASUS VE247H monitor (connected via HDMI). There is also a built-in video - Intel HD Graphics 2000.
I recently started having issues with my second monitor (ASUS). After rebooting the computer, instead of 1920 * 1080, it began to show in 1024 * 768. I went into the resolution settings, returned to 1920 * 1080. On the next reboot, the same thing happened, but now only 1024*768 and 800*600 were in the list of available resolutions. I reinstalled the driver, disassembled / cleaned the computer, changed cables, turned off the discrete video card, etc. After some time, I noticed that higher resolutions appeared in the list of available modes. In general, it somehow worked (it took several hours). And after the next reboot again only 1024*768 and 800*600.
Through the panel, nVidia created a custom resolution, played around with the synchronization - it worked when I chose DWT.
Despite the fact that it’s working now, I want to find out what the problem is, how to return the “native” permissions that have disappeared?
PS If I click "Find" in the resolution settings window, then the second monitor disappears from the system (it is also missing in the list of devices). After that, you have to click "Update hardware configuration" a couple of times in the device manager - the monitor appears again, but the resolution flies again. It would be fine, it just flew off, but it is not in the list of available permissions, although it is present in the list of user permissions - you have to delete and re-create it.
upd: I forgot to mention that in the nVidia panel, the connection method for this monitor is displayed as "DVI", although the actual connection is via HDMI or DP.