Comment 71 for bug 1782984

Rych, as I mentioned before Ilya had expressed issues with other GTK
apps. In particular, the same error appears in /var/log/syslog with
LibreOffice, so that may be somewhere to check:
https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1801161

The one thing to notice about this is that this is a problem with GTK2.
With GTK3, it's implied there are no such problems. We know that LXDE is
not GTK3 compliant. However, SpaceFM seems to be able to support GTK3,
so try that and see if it doesn't fix your problems.

As an aside, PCMan himself abandoned GTK in lieu of Qt since GTK3 was
more of a resource hog. If you want a distro that's non-GTK, go for
Lubuntu 18.10+ as it uses LXQt.