File names arbitrarily changed during Import - why?

Last night as I improted several hundred images from a day of scanning Kodachrome transparencies into 160-180 mb uncompressed digital files, each with its own very specific file name, LR went from importing using the file name I had created to arbitrarily making the file names "untitled-(sequential number).tif". I have imported thousands of digital files from my scanning efforts to lightroom with no change or degradition of file names until this event.

What is more, when I look at the Orignal filename line in Metadata, all I see is the "untitled-(#)" and there is no "original Filename" so it was clearly improted using the "untitled (#)" file name.

Does anyone have any idea what might have happened and why?

I am running Windows 10 and LR, dtgailed system config info is below:

Lightroom version: CC 2015.9 [ 1106920 ]

License: Creative Cloud

Operating system: Windows 10

Version: 10.0

Application architecture: x64

System architecture: x64

Logical processor count: 4

Processor speed: 3.0 GHz

Built-in memory: 32710.1 MB

Real memory available to Lightroom: 32710.1 MB

Real memory used by Lightroom: 3399.8 MB (10.3%)

Virtual memory used by Lightroom: 3517.9 MB

GDI objects count: 911

USER objects count: 2781

Process handles count: 2205

Memory cache size: 6899.8MB / 7921.5MB (87.1%)

Maximum thread count used by Camera Raw: 4

Camera Raw SIMD optimization: SSE2,AVX,AVX2

Camera Raw virtual memory: 2246MB / 16355MB (13%)

System DPI setting: 144 DPI (high DPI mode)

Desktop composition enabled: Yes

Displays: 1) 3840x2160, 2) 3840x2160, 3) 1920x1080

Input types: Multitouch: No, Integrated touch: No, Integrated pen: No, External touch: No, External pen: No, Keyboard: No

Graphics Processor Info:

GeForce GTX 1060 6GB/PCIe/SSE2

Check OpenGL support: Passed

Vendor: NVIDIA Corporation

Version: 3.3.0 NVIDIA 376.53

Renderer: GeForce GTX 1060 6GB/PCIe/SSE2

LanguageVersion: 3.30 NVIDIA via Cg compiler

Application folder: C:\Program Files\Adobe\Adobe Lightroom

Library Path: C:\Users\Tom\Pictures\Lightroom\Lightroom Catalog.lrcat

Settings Folder: C:\Users\Tom\AppData\Roaming\Adobe\Lightroom

Installed Plugins:

1) AdobeStock

2) Canon Tether Plugin

3) Facebook

4) Flickr

5) Leica Tether Plugin

6) Nikon Tether Plugin

7) Perfect B&&W 9

😎 Perfect Effects 9

9) Perfect Enhance 9

10) Perfect Photo Suite 9

11) Perfect Portrait 9

12) Perfect Resize 9

Config.lua flags: None

Adapter #1: Vendor : 10de

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