NFS mount shows root directory after some time

Question

I have some NFS4 shares mounted via autofs. E.g. /mnt/autofs/MyPictures When I navigate in this directory, e.g., going to /mnt/autofs/MyPictures/2017-01/partyWithHugh, after some time, Nautilus shows again the root folder (/mnt/autofs/MyPictures). Why is that and how can I prevent this?

$ nautilus --version
GNOME nautilus 3.26.0

$ less /etc/auto.master
+auto.master
/mnt/autofs     /etc/auto.nfs   --ghost

$ less /etc/auto.nfs
MyPictures   -fstype=nfs4,rw,soft,intr,async,noatime 192.168.0.107:/MyPictures