FIJI bug - program changes or adds images within stack

Strange behavior of FIJI (version 2.1.0/1.53c on 2019 iMac running OS 10.15.5) with ‘manually’ created stacks (Image-> Stacks-> Images to Stack):

  1. Program replaces first image in stack with a copy of the last image in the stack. I believe it occurs after adding images to a stack (Image-> Stacks-> Add Slice), then a Crop and/or Adjust-> Size, although can’t always reproduce it.
  2. While using Image-> Stacks-> Tools-> Concatenate… (to join two such ‘manually’ created stacks), a similar error can occur in which the final image of the stack is added to the top of the stack. (I don’t believe the first image is replaced in this case - instead, a slice is added to the beginning of the stack.)