Focus stacking overwriting previous stacked tiff

Hello
I am an enthusiast and am a very basic photoshop user, I shoot my orchids using Focus stacking. I was happy till a couple of months ago with my workflow

1. I use the Nikon D850 built in option to shoot stacked images. Usually varies from 20-50 raw exposures
   Images are imported into lightroom classic 
2. The images to be stacked are selected in lightroom and sent to photoshop as layers. Edit in > Open as Layers in Photoshop
3. I have a saved action in Photoshop that has the following commands. Select all layers > Align layers > Auto blend layers > Flatten image > Save
4. The new tiff file used to be written in the original source directory and would show up in the lightroom catalogue as the last but one image{If I stack 20 images the tiff would show up as the 20th image and the last raw would appear as the 21st image}
5. I keep the tiff and delete the raw files
   
   
   Till about a couple of months back everything was fine. Now whenever I stack a set of images the workflow is fine and the tiff gets saved. But when I stack the next set of exposures  it gets saved with the same name as the first stacked tiff and the first one gets overwritten without any prompt or warning. All the new images end with the name ShootNameYYYYMMDD-DSC_4726-Edit
   
   
   Does anyone else face this problem? Is this a known issue or is this a problem that I have created?