Various tray icons are highly distorted after one changes panel scaling

[LinuxOnTheDesktop]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Go to Settings -> Panel
2. Change the scaling from 'optimal' mode to 'exact mode'.
3. Look at panel.

Expected behavior Clearly, this is undesirable.

Frequency Does the issue happen:

• [X ] Always
• [ ] Randomly

Edition (Desktop environment): In which edition is this happening?

• [X] Cinnamon Edition
• [ ] MATE Edition
• [ ] Xfce Edition

Live or post-install: Indicate if this is happening after the installation, or during the live session:

• [X] Post-install
• [ ] Live session

Screenshots If applicable, add screenshots to help explain your problem.

Before changing scaling:

After:

Locale: Paste the output of locale.

LANG=en_GB.UTF-8
LANGUAGE=en_GB:en
LC_CTYPE=en_GB.UTF-8
LC_NUMERIC=en_GB.UTF-8
LC_TIME=en_GB.UTF-8
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY=en_GB.UTF-8
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER=en_GB.UTF-8
LC_NAME=en_GB.UTF-8
LC_ADDRESS=en_GB.UTF-8
LC_TELEPHONE=en_GB.UTF-8
LC_MEASUREMENT=en_GB.UTF-8
LC_IDENTIFICATION=en_GB.UTF-8
LC_ALL=

Drivers: Paste the output of inxi -Gxx.

Graphics:  Device-1: Intel UHD Graphics 620 vendor: Lenovo driver: i915 v: kernel bus ID: 00:02.0 
           chip ID: 8086:5917 
           Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa 
           compositor: muffin resolution: 2560x1440~60Hz 
           OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) v: 4.5 Mesa 19.0.2 
           compat-v: 3.0 direct render: Yes 

Crash report:

''Stack trace'' If you are reporting a crash. Go to "Software Sources" and enable the debug symbols. Then go to "System Reports" and extract the stack trace for your crash and paste it here.

''Dmesg'' If you type dmesg in a terminal, you should see a line corresponding to the crash. Paste it here.

Additional context Add any other context about the problem here.

• The other distorted tray icons are respectively those of Dropbox and Ulauncher.

• Restarting Cinnamon fixes the problem. I think I saw something about that in a fairly recent bug report - or commit comment or pull request - by one of your developers.

• The scissor icon - for the program CopyQ - is not right even before changing the scaling (and I filed a bug against CopyQ for that).

More on my system

OS: Linux Mint 19.1 Tessa x86_64 Host: 20KHCTO1WW ThinkPad X1 Carbon 6th Kernel: 5.2.3-050203-generic Uptime: 6 hours, 51 mins Packages: 3155 (dpkg), 6 (flatpak), 3 (snap) Shell: bash 4.4.20 Resolution: 2560x1440 @ 60.01Hz DE: Cinnamon 4.2.3 WM: Mutter (Muffin) WM Theme: Mint-Y-Dark-trans (Mint-Y-Dark-BB_hack) Theme: Mint-Y-Dark [GTK2/3] Icons: Paper [GTK2/3]