itimpi

Sounds as if you have been emulating that missing disk ever since without realising it 😒.  It is a common misconception that unassigning a disk is all that is required not realising that doing so will make Unraid treat it as a failed disk and start emulating it.   To stop this happening you need to follow the correct procedure to remove a disk from the array as documented here in the online documentation accessible via the ‘Manual’ link at the bottom of the GUI or the DOCS link at the top of each forum page.
 

Try removing the Mover Tuning plugin.

What about the power to the drive?    The noises could be an indication of insufficient power.  Do you use power splitters to get enough connections - they can cause problems.   You could try swapping the power cables with another drive to see if the problem stays with the drive or moves with the cable change.

Unless you have a very old CPU then doing 2 parity drives at the same time can run at a similar speed to doing a single one.   If the new parity drive is slower, that WILL slow things down as the speed is determined by the slowest drive at any point in the check.   I wonder if the new WD parity drive is using SMR technology rather than CMR as that could make a big difference .

According to the SMART report the drive failed the extended SMART test which indicates it should be replaced.

Your ‘system’ share is on disk1 so if you run any docker containers or VMs you will get the symptoms you describe.    You really want this share to be only on the cache pool.  You need the docker and VM services temporarily disabled to be able to move it as they keep files open in that share

The logs in the diagnostics start over every time the system is booted.    You would need to enable the syslog server to get a syslog that survives a reboot so we can see what lead up to the crash.
 
The commonest cause of instability seems to be using macvlan with docker so it might be worth checking for that.   The easiest solution is to switch to using ipvlan instead.

It looks like your ‘system’ share has files on disk3,   This means that if the docker or vm services are enabled disk3 and parity will be spun up most of the time.   You want to get all the contents of this share onto the ‘cache’ pool to avoid this and to maximise performance.
 
you also have a lot of .cfg files in the config/shares folder on the flash drive for shares that currently do not exist.    Deleting these will tidy up that part of the diagnostics and make it easier to spot relevant information. 

You need to contact support to get them to do this for you.

That suggests that you have something generating spurious keyboard input.

Yes.

I would suggest that you contact support giving the GUID for the new flash drive and they should be able to help you.

The problem will be that Unraid sets the start sector for the partition on the drive differently for SSD and HDD so the available space is not actually the same.

You should not have done step 4).   You would have got a pop up warning that this would create an empty file system; update parity to reflect this; and was not part of any data recovery process.   Without step 4) your data would have been rebuilt onto the replacement drive.
 
the correct process to use is documented here in the online documentation accessible via the ‘Manual’ link at the bottom of the GUI or the DOCS link at the top of each forum page.

Stop array unassign parity1 ready to make Unraid forget current assignment start array to commit change stop array assign parity1 start array to sync both parity drives

When it gets written to will depend on the Allocation Method you have selected for the share and how full your current drives are.   It can be some time!   You could manually create a folder corresponding to the share name on the drive if you want to force it to show up early.

If the file is located in the ‘system’ share (which is the default), then the linked process would work.   Alternatively you could use the Dynamix File Manager to do it manually.

Lots of the array drives started simultaneously getting errors and they do not show up in the SMART reports so they went offline.   This suggests a problem with something they share such as power or the HBA they are attached to.

That looks good.   Can you get anything off the old flash drive?  If so the contents of the ‘config’ folder are what you want.   That would allow you to avoid reconfiguring things as you could then copy its contents to the new flash drive.
 
Regarding changing the licence if you have your original licence file put it in the ‘config’ folder on the new flash drive and when Unraid boots it should take you through the process for transferring the licence to the new drive.  If you have any problems with this then you will need to contact support.
 
It is always a good idea to have a backup of your flash drive.   You can always make one manually either by copying the contents on a PC/Mac or (probably more convenient) clicking on the Boot drive on the Main tab and selecting the backup option.    In terms of automated backups then you can periodically make one locally on the server using the appdata backup plugin, or on the cloud by installing the Unraid connect plugin (used to be called MyServers).

That is expected behaviour if you have Exclusive Shares enabled and meet the conditions on a particular share for it being Exclusive.   The /mnt/cache/xxx path is more efficient than going via /mnt/user/xxx as it bypasses the Fuse layer in Unraid.   This is described in the GUI help for the Exclusive setting under Settings->Global Share Settings

These are automatically created if docker and VMs are enabled.

To get best performance for docker containers and VMs you want this share to be on the cache (i.e. mover to be array->Cache).    
 
You can get even better performance if once the whole share is on the cache you remove the secondary storage option and under Settings->Global Share settings you enable the option for Exclusive Shares as this bypasses the Fuse layer in Unraid that is otherwise used to manage User Shares.

Actually it tells you nothing about the cables as the test is completely internal to the drive.
 
the process for re-enabling the drive is covered here in the online documentation accessible via the ‘Manual’ link at the bottom of the GUI or the DOCS link at the top of each forum page. The Unraid OS->Manual section in particular covers most features of the current Unraid release.
 

Contact support
 

The SMART information for that drive looks very bad as it has lots of reallocated and pending sectors - both of which you really want to be 0 for reliable operation in Unraid.   I would replace ASAP.