Lightroom Classic Stacking Issue, cannot stack more than two photos

I'm having stacking issues in Lightroom Classic CC after updating. Previously I was able to export a RAW NEF file with the new JPG file added below, and then export a second exported JPG file again, adding additional settings, name, and a watermark with the same "add below original" - creating a stack of three with the RAW NEF as the top of a stack of 3.

Now it's creating a stack within the stack. With original selected pressing the "S" key or menu "Expand all Stacks" only expands the original from the first export with its own stack icon square with a 2 in a box but not the additional watermarked file. Selecting the Exported file with a "2" in the expanded stack and pressing the "S" key only collapses the stack. Only by selecting the first exported JPG file and using the menu "Expand all Stacks" on can I again see the three associated files. Suffice to say my process has now required an additional menu step to view/edit. More laboriously: Switching to view by capture time, Ungrouping the stack, Selecting in the proper order, then regrouping as a stack of the 3 images, then switching back to View by Rating each time I create a watermarked third file.

It seems the export option "Below Original" now stacks the second export of my first export (without watermark etc) to the first exported JPG (no watermark) instead of the "Original" NEF RAW file into a group of 3 associated images as the previous version of Lightroom CC did before it became "Classic".

While viewing by Rating the files unstack out of order: Final JPG w/watermark, Original NEF, Exported JPG. Switching to Capture time displays them as: Original, Exported, Watermark. Expanding the stack within a stack requires extra clicking/menu hunting and is hardly intuitive. Only by ungrouping stack and regrouping as a stack of 3 can I view them as I had in the past.

The confused order when viewing by rating which switches them around and required extra workarounds has me pulling my hair out when the previous version conveniently left them in a single stack in the order of creation even when viewing by rating - allowing me to more easily edit, export, and watermark my images without many, many more keystrokes and mouse clicks. I have permanent nerve damage from a repetitive strain injury earned from a lifetime of computer use — added user interface interactions like this make my life more painful. I'm trying to figure out some macro shortcuts to avoid some of this clunkiness but mostly I've just become frustrated by the new "feature". Though there may be some usefulness to stacks within stacks this has made my life far more difficult.

PLEASE HELP!!

I assume you mean Export with 'Add to Stack' checked,

I'm seeing a more serious issue!

If I export to JPEG with FileName-1.jpg it file is stacked with the original file. If I then export a 2nd JPEG file with FileName-2.jpg it is stacked with the original. The 1st JPEG file (FileName-1.jpg) becomes unstacked and appears as the last picture at the end of Grid view. Changing Sort Order to Capture Time or File Name or A>Z, Z>A has no effect. The file remains in the end position of Grid View as the last picture.

If I export a 3rd file (FileName-3.jpg) it is stacked with the original and the FileName-2.jpg appears at the end of the Grid view below FileName-1.jpg. If I right-click on the original file (1 of 2) and select 'Stacking>Unstack' all of the files appear together as expected. Very strange behavior!

I checked LR CC 2015.12 using the same image file in the same folder structure and it behaves normally as expected with all files stacked below the original.

I'm on Windows 7 running LR Classic 7.0.1. Anyone else seeing this behavior?