Subject column in "sent" folder twitching, constanly re-sizing, when showing a messag

Win 10 fully updated. FF 61.0.1. Webmail build 2018-08-07T07:42:43.760Z.

  1. Webmail is open in Inbox.
  2. Refresh browser page (F5).
  3. Go to “sent” folder.
  4. Click to display a message (first, second message same behavior).
  5. The Subject folder start cycling between two column widths so that the Subject and Size columns are “hopping” (the picture attached obviously cannot show the dynamics but you can see the amount of displacement).
  6. If you narrow the list to half default, this behavior will stop.
  7. I can repeat this. Cannot see it in any other folder however.

In the version of 11 august the columns are no longer resized automatically based on their content width. Instead the widths are only reduced if the display is narrower, and restored back to the widths set by the user if the display is wide enough. (If you resize a column manually - the width is stored, and will be used to restore width).