Tray Icons for some programs are not displayed until Cinnamon is restarted

Issue

Thunderbird tray icon (via either of the addons "MinimizeToTray Reanimated" or "FireTray" (this TB 60 compatible fork)) and Shutter tray icon are not being displayed. See screenshot below.

They do show after restarting Cinnamon via ctrl-alt-esc (top: FireTray, bottom: MinimizeToTray Reanimated):

Also, if Shutter is quit while Thunderbird is still running, the tray seems to perform an update that is different from what it does when the programs were first launched or Cinnamon is restarted. The result looks like this:

Steps to reproduce

see above

Expected behaviour

Correctly display the icons.

Other information

system

 * Cinnamon 4.2.4, not using daily builds PPA
 * Mint 19.2 Cinnamon
 * NVIDIA GeForce GTX 670; NVIDIA driver, version 390.116
 * 64 bit

~/.xsession-errors

Cjs-Message: 07:26:54.150: JS LOG: [LookingGlass/info] Adding systray: thunderbird (24x24px)
Cjs-Message: 07:26:54.151: JS LOG: [LookingGlass/info] Resized thunderbird with normalized size (24x24px)
Cjs-Message: 07:26:58.910: JS LOG: [LookingGlass/info] Adding systray: shutter (24x24px)
Cjs-Message: 07:26:58.911: JS LOG: [LookingGlass/info] Not resizing shutter as it's known to be buggy (24x24px)
Cinnamon warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x7400099 (Session - )
Cinnamon warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x7400099 (Session - )

Reproduce the missing Thunderbird and Shutter icons on Cinnamon 4.2.4, then start from the systray messages in ~/.xsession-errors, especially the “Adding systray” and resizing entries. Trace the tray update behavior during startup, application exit, and Cinnamon restart; done means both icons appear and update correctly without restarting Cinnamon.