@EnduranceCode: Lubuntu 18.10 does not use LXDE, but LXQt, so it's not
PCManFM, but PCManFM-qt. It does not suffer this problem because as
suggested in the last few comments, the problem seems to be related to
GTK and particularly GTK2. LXDE is still not GTK3 compliant, but if it
was, I believe that would solve this problem. You might want to check
and see if you have the errors reported above, as that would again go a
long way to further confirm this.
@EnduranceCode: Lubuntu 18.10 does not use LXDE, but LXQt, so it's not
PCManFM, but PCManFM-qt. It does not suffer this problem because as
suggested in the last few comments, the problem seems to be related to
GTK and particularly GTK2. LXDE is still not GTK3 compliant, but if it
was, I believe that would solve this problem. You might want to check
and see if you have the errors reported above, as that would again go a
long way to further confirm this.