GJS now warns about objects that have been freed in C. This has caused numerous traces like this:

Object Shell.GenericContainer (0x55f8a82e3fa0), has been already finalized. Impossible to get any property from it.

== Stack trace for context 0x55f8a51c2170 ==
#0 0x7ffd716fe7a0 b   resource:///org/gnome/shell/ui/tweener.js:73 (0x7fd327dddef0 @ 9)
#1 0x7ffd716fe840 b   resource:///org/gnome/shell/ui/tweener.js:105 (0x7fd327ddf230 @ 36)
#2 0x7ffd716fe8e0 b   resource:///org/gnome/shell/ui/tweener.js:92 (0x7fd327ddf098 @ 52)
#3 0x7ffd716ff800 b   resource:///org/gnome/gjs/modules/tweener/tweener.js:203 (0x7fd327de9cd0 @ 54)
#4 0x7ffd716ff950 b   resource:///org/gnome/gjs/modules/tweener/tweener.js:332 (0x7fd327de9d58 @ 1626)
#5 0x7ffd716ffa00 b   resource:///org/gnome/gjs/modules/tweener/tweener.js:345 (0x7fd327de9de0 @ 100)
#6 0x7ffd716ffa90 b   resource:///org/gnome/gjs/modules/tweener/tweener.js:360 (0x7fd327de9e68 @ 10)
#7 0x7ffd716ffb10 I   resource:///org/gnome/gjs/modules/signals.js:126 (0x7fd327de2b38 @ 386)
#8 0x7ffd716ffbc0 b   resource:///org/gnome/shell/ui/tweener.js:208 (0x7fd327ddf808 @ 159)
#9 0x7ffd716ffc20 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd327dc2bc0 @ 71)
#10 0x7ffd716ffc20 I   resource:///org/gnome/shell/ui/tweener.js:183 (0x7fd327ddf780 @ 20)
#11 0x7ffd716ffcc0 I   self-hosted:917 (0x7fd327dee5e8 @ 394)

I also see some starting from tweener.js:80.

I'm using gnome-shell from ArchLinux which is at git version 64c857e3.