SMART error Device: /dev/sda [SAT], 2 Currently unreadable (pending) sectors but which ones?

Question

I have a proxmox installation on a PC, which daily reports this to me via email:

Device: /dev/sda [SAT], 2 Currently unreadable (pending) sectors

Until some days ago it was only one, so I guess it's the hard drive starting to fail (even if it's only a couple months old).

Trying to figure out how to discover which are the broken sectors, in order to avoid reading from them, I found some thread here and there, stating to run these commands, which I'm pasting the output of:

smartctl -t long /dev/sda

followed by (some minutes later)

$ smartctl -l selftest /dev/sda
smartctl 7.2 2020-12-30 r5155 [x86_64-linux-5.13.19-2-pve] (local build)
Copyright (C) 2002-20, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF READ SMART DATA SECTION ===
SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed without error       00%       997         -
# 2  Short offline       Completed without error       00%       849         -
# 3  Extended offline    Completed without error       00%       849         -
# 4  Extended offline    Completed without error       00%       828         -

As you can see, no LBA_of_first_error is given, so I don't know what are the damaged sectors.

Moreover, this command gives no error:

$ dd if=/dev/sda of=/dev/null
500118192+0 records in
500118192+0 records out
256060514304 bytes (256 GB, 238 GiB) copied, 534.688 s, 479 MB/s

How can I resolve this problem? (except throwing away the defective hard drive)

Thanks in advance