Sorry this happened. It is likely a update issue from MacOS not flushing the cache on the volume correctly at shutdown/restart after the install. As a result, the directory gets corrupted, apparently. At least the same mechanism happens to HFS.

Every MacOS upgrade, there are users who complain their external volumes no longer mount. MacOS runs an auto repair on all volumes in HFS or APFS format on restarting, which probably fixes most directory issues at mount time. But when it fails, the volumes are left unmountable or read only.

Because of the amount of users I encounter, I see these a fair amount. I also see APFS volumes that can no longer mount, always "external" volumes. I also see the oddity of connecting those volumes to a different system, enables them to mount (possible they can clear some flag that is preventing the volume from unwinding to the last mountable state)

SoftRAID does not ever initiate writes of data. When MacOS wants to write to a disk, the SoftRAID driver passes the read/write requests to "disktool", which performs the actual reads and writes to the disks. It was designed this way to avoid any potential driver compatibility issues.

So while I do not know what happened to your volume, my guess it is a side effect of the MacOS upgrade. Back around 10.3 or 10.4, when MacOS had the disaster of damaging many thousands of users external drives, I never upgrade MacOS with any externals attached. Just cautionary, but I recommend all users to do this.

This is a directory issue. I hate ExFat as moving it from Windows to mac can result in easy degradation of the directory. We just removed direct support for this in SoftRAID Mac for this reason. One of the reasons is ExFat has no backup directory, so is more susceptible to directory damage than HFS or NTFS. (or so I am told by engineering)

You need to erase and restore from backup, or run a recovery application like R-Studio, EaseUS or perhaps Disk Drill. All three should have a trial mode to try with.

there are no "repair" utilities that I know of that run in MacOS for ExFat file systems. there may be in windows, I do not know.

Please also attach a SoftRAID Technical Support file (from this current system), so we can look for oddities.

I will try creating a second volume this weekend

Support file is attached. 

Thanks!

Please also attach a SoftRAID Technical Support file (from this current system), so we can look for oddities.

Every hour? We may need to create a debug tool to investigate, but I will bring this into engineering for investigation. There should not be hourly crashes by the tool (A kernel panic is when the machine restarts).

Can you try a clean install, in a second volume. I believe you will see this is something in your System.

Run Disk Utility. Click on your internal boot disk, click + volume. Select APFS. restart into recovery mode and "reinstall MacOS". Point it to this new volume.

this does not affect your existing system at all. You can set startup just like if it were a separate disk. Now, if this is an hourly thing, it should be easy to test. thanks!

This is not a kernel panic. this is the SoftRAIDtool crashing, i.e, the Application "crashes", or the SoftRAID Monitor crashed, correct?

Honestly, I don't know what's crashing when that alert pops up. All it says is "SoftRAID Tool" crashed. My Thunderbay 4 is still accessible and I can open up SoftRaid Monitor without any problems. That error pops up every hour like clockwork, though. 

This is not a kernel panic. this is the SoftRAIDtool crashing, i.e, the Application "crashes", or the SoftRAID Monitor crashed, correct?

Attach a SoftRAID tech support file. The Thunderblade should always be mountable. My guess is the directory is damaged, it has nothing to do with SoftRAID's driver, or Sonoma.