kwrite delays detection of a second modified file

Create two files
$ echo 1 > A
$ echo 1 > B

Edit them in kwrite
$ kwrite A B &

Return to terminal and modify the files:
$ echo 2 > A
$ echo 2 > B

Click on the kwrite window for A. Get "File has changed on disk" popup. Click "Reload".
Click on the kwrite window for B. Do not get expected "File has changed on disk" popup!
Click on the kwrite window for A. No popup (as expected).
Click on the kwrite window for B. Only now do we get "File has changed on disk" popup!

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: kwrite 4:15.12.3-0ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-116.140-generic 4.4.98
Uname: Linux 4.4.0-116-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
CurrentDesktop: XFCE
Date: Fri Mar 16 10:20:29 2018
InstallationDate: Installed on 2013-08-21 (1667 days ago)
InstallationMedia: Ubuntu 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130214)
SourcePackage: kate
UpgradeStatus: Upgraded to xenial on 2017-04-03 (346 days ago)