JorgeB

Change enable docker to yes, it should create the paths on first start. 

If the log tree is the only problem this may help, with the array started type:
btrfs rescue zero-log /dev/mapper/sdf1 Then re-start the array.

You should fix the ATA errors first, they are most likely a power/connection problem, then check filesystem from the GUI, without -n.

Looks more like a power/connection problem.
 
I would do a new config with old disk1, after checking/replacing cables, or using a different PSU.

Check filesystem to see if it still can be fixed:
 
https://wiki.unraid.net/Check_Disk_Filesystems#Checking_and_fixing_drives_in_the_webGui

Log is full of spam so cannot see the beginning, run another non correcting check to see if it finds the same errors, if yes correct them.

Disk doesn't even show a valid SMART report, try swapping cables with known good ones but most likely the disk is bad.

Go to Settings - Docker and specify the image file, e.g:
 
/mnt/cache/docker/docker.img

Everything looks normal, only thing I see that raises a concern are the controllers, the LSI in IT mode is fine, though the firmware should be updated, but there's also an LSI MegaRAID controller, there could be something with the write cache or config that is slowing down the writes, and please note that RAID controllers are not recommended in general.

Docker image is corrupt, delete and re-create.

Server is running out of RAM, try limiting more the RAM for VMs and/or docker containers, the problem is usually not just about not enough RAM but more about fragmented RAM, alternatively a small swap file on disk might help, you can use the swapfile plugin:
 
https://forums.unraid.net/topic/109342-plugin-swapfile-for-691/

Use -L

Filesystem as other issues other than just the log tree, backup and re-format.

Run a correcting check, then a non correcting one without rebooting, if the 2nd one finds new errors post new diags.

Try this:
https://forums.unraid.net/topic/118286-nvme-drives-throwing-errors-filling-logs-instantly-how-to-resolve/?do=findComment&comment=1165009
 

It's up to you, if the server is not being heavily used probably the same risk to leave it on, btw the disk dropped offline, most likely a power/connection issue, but since it dropped there's no SMART report.

Yes, do that.

If the log tree is the only problem this may help:
btrfs rescue zero-log /dev/sdb1  
Then re-start the array

Parity is SMR, so it will slowdown all writes.

Make sure the shares are being exported, default is no, click on the share(s) and scroll down to Export:

If Docker/VM services are using the cache pool disable them, unassign all cache devices, start array to make Unraid "forget" current cache config, stop array, reassign all cache devices (there can't be an "All existing data on this device will be OVERWRITTEN when array is Started" warning for any cache device), re-enable Docker/VMs if needed, start array.

Yep.

It's a logged as a disk error, and the disk has pending sectors, so likely it's failing, you can run an extended SMART test to confirm.

Disk needs to be replaced.

Create a new flash drive and restore the config folder, that's all you need, then need to replace the key.