Dell Encryption corrupted Truecrypt container

On external USB hard drives I have two copies of old Truecrypt containers which contain personal and work files dating back 20 years.  My current work Dell laptop (Windows 10) uses Dell Data Security with full encryption.

Truecrypt is also installed on my work laptop because my company formerly used it for disk encryption, but they no longer use it.  So I'm able to open my personal Truecrypt containers using my work PC, which is useful when I want to reference technical materials that I have in these personal containers in order to use that information  in my work.

Each time an external storage device is connected to my work laptop, the Dell Data Security program pops up a dialog giving the user a choice either to immediately begin encrypting all files on the external device, with R/W access being granted upon completion of encryption, or alternatively not to encrypt anything but to allow only read only access to the external device.  This hasn't caused any problems and I always select the "read only" option.

The problem I'm posting about occurred when using Truecrypt to mount one of my Truecrypt containers.  On Windows, Truecrypt mounts one of its containers as a drive with a drive letter.

Although the device containing the Truecrypt container was mounted read only (me having chosen that option on connection), and no dialog popped up when I mounted the Truecrypt container, I believe Dell Data Security silently started to encrypt the files in the Truecrypt container as soon as it was mounted to a Windows drive letter.  I infer this is the case because in one of my two copies of the Truecrypt container, the top 15 folders, by alphabetical order, seem to have been unrecoverably encrypted.  The files and folders are still there with the original filenames, but each file is filled with what looks like encrypted garbage data (verified by looking at files that were originally plaintext).  In that same container, files in the 16th and subsequent folders remain unencrypted and accessible.  I think that is because, whenever this occurred, I either dismounted the Truecrypt volume or shut off the machine after Dell Data Security had finished encrypting the 15th folder but before it got to the 16th.

Although I infer Dell Data Security seems to have encrypted the files in these top 15 folders, Dell Data Security doesn't now detect that they're encrypted or know how to display unencrypted versions of them the way it seamlessly decrypts files on my C: drive.  There is no decryption executable in the container.  So from my POV the contents of these files are now completely inaccessible.

As for the second copy of my Truecrypt container, on a different external storage device, it is now unmountable.  I fear this is because I attempted the same thing with this container, but left it connected longer, so that Dell Data Security was able to get to some level of completion where it corrupted the container's envelope somehow.

Would be grateful for any advice on how to try to get my work laptop to decrypt these inadvertently encrypted files, and wonder if a change can be made so that this kind of mounted drive can at least have a dialog pop up when it is mounted.

Thanks,

Brad