The target disk is too small for this operation, possibly due to partition map limits. : (-69519)

Ok, I found a little bit of time to experiment.

First you need to get the proper disk identifier for the APFS Container of your macOS installation. I'm assuming you do not have a Fusion Drive since that may change things. Assuming you have only a single internal drive holding macOS, then you can get the drive identifier of the hidden APFS Container by using the following Terminal command:

diskutil  list  internal  |  grep  'Apple_APFS'  |  awk  '{print $NF}'

This will give you a drive identifier in the form of "diskXsY", such as "disk0s2".

You will use the drive identifier you got from the last command in the next command....here is the template (the last character is the number zero):

diskutil  ap  resizeContainer  diskXsY  0

So if you received the drive identifier of "disk0s2", you would replace "diskXsY" in the template command making it into this:

diskutil  ap  resizeContainer  disk0s2  0

Or, Here is a single line command to perform the operation automatically......it assumes no Fusion Drive and only a single physical internal drive with just one APFS Container and and an item called "(free space)":

drive="$(diskutil  list  internal  |  grep  'Apple_APFS'  |  awk  '{print $NF}')"; diskutil  ap  resizeContainer  $drive  0

Everything must be typed exactly or you may get unexpected & unintended results. The last character is a zero. I tested the command on a .dmg file I created to simulate a single physical drive system with an APFS Container and "(free space)" such as after deleting the Windows Bootcamp partition.

If you have a Fusion Drive setup or multiple internal drives, then we will need the output of the following command in order to modify the instructions for you:

diskutil  list  internal

Thanks for providing that information. You do indeed have a Fusion Drive setup.

Before doing anything else, make sure you have a good backup of your data on the macOS DATA volume since any commands to manipulate the partitions on the drive could go awry & cause you to lose access to the internal Data volume & may make your main OS installation unbootable.

You will need to reference the hard drive portion of the Fusion Drive which is the one located on the 2TB internal drive. At the time you ran the "diskutil list internal" command, the identifier required for the resize command is "disk1s2" since that is the identifier for the APFS Container directly ahead of the "(free space)" item. Make sure you confirm this identifier before running the following command to attempt to merge the "(free space)" item into the APFS_Container located on the 2TB hard drive (replace "disk1s2" with the current identifier if it has changed since the last time):

diskutil  ap  resizeContainer  disk1s2  0

Unfortunately the other "automated" option to identify & resize won't work here because you have two physical internal drives with APFS Containers & I'm not sure of a simple method of filtering for the proper one.....especially for a simple single command. As long as you confirm the identifier for the APFS Container on the 2TB internal drive and use that value in place of "disk1s2" in my example, then it should work.

I would try booting into Recovery Mode (Command + R) to run Disk Utility First Aid on the Fusion Drive item and on the hidden APFS Container. Within Disk Utility you will need to click "View" and select "Show All Devices" before the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok", click "Show Details" and scroll through the report to see if any unfixed errors are listed. If so, then run First Aid again until the errors are gone. If the errors remain even after several attempts, then they cannot be repaired. Those errors are may be the problem. In that case, you would need to perform a clean install of macOS by first erasing the Fusion Drive followed by reinstalling macOS & restoring from a backup.

If First Aid is able to repair the errors, then you can try the resize option again while still booted into Recovery Mode. The Terminal app can be found on the "Utilities" menu on the menu bar....you will first need to quit the Disk Utility app to return to the main recovery mode screen. Remember to confirm the drive identifier for the APFS Container located on the 2TB drive before trying to resize it.

Another possibility is the hard drive portion of the Fusion Drive is failing. You can try running the Apple Diagnostics to see if any hardware issues are detected, however, it is unlikely it will detect anything other than the most severe issues. You can check the health of the drives while booted into macOS by running the third party app DriveDx (free trial period) and posting the complete text report for each internal drive (SSD & Hard Drive....especially the HD) by using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

Unfortunately if Bootcamp Assistant did not proper re-merge the Windows Bootcamp partition back into the main Apple partition/Container, then you will need to start completely over by performing a clean install of macOS by first erasing the whole drive (or Fusion Drive item if so equipped) followed by reinstalling macOS & restoring from a backup.

While Disk Utility should technically & theoretically be able to re-merge the "free space area", unfortunately in the real world this just does not seem to happen (Disk Utility is not a very good app).

If you are familiar with the command line, then you may be able to use the "diskutil" command to merge the "free space area" into the main partition/Container (or Fusion Drive). I don't know the proper options to use. I do know another user I was assisting did provide the proper command & options several years ago (they corrected my suggestion since I didn't get it quite right), but I don't recall the specifics now. I don't the time or a spare drive to experiment.

It seems like the hard drive may have some issues with the write head flying too high & causing errors, otherwise the drives appear Ok.

If you ran First Aid multiple times and those errors remain, then First Aid is unable to fix them. It is certainly possible those "Warnings" may be preventing the merging of the free space section to the APFS Container. If those errors/warnings are associated with an AFPS snapshot, then once the snapshot is deleted those errors/warnings should also go away. It the snapshot is associated with a Time Machine backup or other backup, then you can try deleting the particular snapshot if the backup has already been successfully transferred to external media. If the snapshot is related to the OS "update" volume, then once the next OS update (perhaps even software update) has been installed which requires a system reboot, then that OS related snapshot should be gone as well. I guess you could try deleting the APFS snapshot even if it is related to the OS update (no idea whether macOS will allow it). Otherwise you will need to start completely over by first erasing the Fusion Drive followed by reinstalling macOS & restoring from a backup.

View APFS snapshots in Disk Utility on Mac - Apple Support