Volume Hash Mismatch: MacBook Pro

The picture of your First Aid report does not show or mention any "Volume Hash Mismatch" error. It only shows one set of errors "error: btn: invalid btn_flags (0x6f), given btree node is not a root". If macOS gave a "Volume Hash Mistmatch" error and mentioned reinstalling macOS, then you should do that as mentioned by @leroydouglas. Unfortunately the macOS message does not indicate whether you should reinstall macOS over top of itself or perform a clean install by first erasing the whole SSD.

I believe macOS is referencing the latter option. Usually to fix a file system issue that First Aid cannot repair involves erasing the whole physical SSD as GUID partition and APFS (top option). Then reinstall macOS and restore from a backup.

You should always have frequent and regular backups of your computer and all external media (including the cloud) which contains important & unique data.

Try booting into Internet Recovery Mode using Command + Option + R to attempt to access the online Monterey installer. However, some Macs may only be able to access the online installer for the OS which originally shipped on the Mac from the factory which in your case is macOS 10.12 Sierra.

If you are only being presented with macOS 10.12 Sierra when booting with Command + R or Command + Option + R, then you will need to erase the whole SSD before proceeding since you have Monterey installed already. Technically you may be able to create a new APFS volume within the same hidden Container, but this will lead to confusion because Monterey utilizes a lot more APFS volumes than Sierra so those other volumes would need to be deleted in order to recover the storage space. If you want to (or have to) install Sierra, then you may need to change the computer's date & time to some time in 2017 as this error may indicate an outdated certificate included in the Sierra installer. While booted to the Sierra installer launch the Terminal app from the Utilities menu and use this command to set the date & time to Jan. 2, 2017 @ 11:33am:

date  -u  0102113317

If you can boot this Mac normally or into Safe Mode, or if you have access to another Qualifying Mac, then you can create & use a bootable macOS USB installer instead using the instructions in this Apple article:

How to create a bootable installer for macOS - Apple Support

A Qualifying Mac means the Mac used to download the macOS installer must also be compatible with that OS. So to download macOS 12.x Monterey requires a Mac from 2015 to 2022. This article shows which versions of macOS are compatible with various Apple hardware so you can find another model that is compatible with macOS 10.13 (most Macs from 2010 to 2018) if you don't have access to another 2015+ Mac for Monterey:

https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

PhotographerInNL wrote:

Hi,

I have a MacBook Pro 15-inch 2017 that all of a sudden has a serious error, rendering it (almost) completely useless.

The error is: "Volume Hash Mismatch. Hash mismatch detected on volume disk1s5. MacOS should be reinstalled on this volume".

Ok so did you: "...MacOS should be reinstalled on this volume". ?

Reinstall the macOS on top of your existing mac OS for refreshed copy— and compare your results.

How to reinstall macOS

Recovery (both M1 and Intel) — How to reinstall macOS - Apple Support