Your logs payed off: it looks like the Samsung T5 is being skipped according to this entry in the log.
Something I already guessed, but wanted to see proof of.
Oct 14 16:54:19 volumiojm kernel: scsi host0: uas Oct 14 16:54:19 volumiojm kernel: scsi 0:0:0:0: Direct-Access Samsung Portable SSD T5 0 PQ: 0 ANSI: 6
The disk is UAS compatible, resulting in it not being treated like a normal removable usb disk.
It is reported as an internal device instead, currently internal disks are skipped from indexing.
Now, there is a fix for that, but this will likely not make it into Volumio 2 anymore.
Meanwhile there is a Volumio 3 beta version out which fixes it.
That version is actually one update newer than the RC1 - Open Beta Testing version which was announced today.
In case you want to test it, flash this version to an SD card and have a go.
When you decide to test it, let me know the result.
As soon newer RC versions become available, you should be able to update it using the system menu without loosing any data.