samba - Dec 2018 - Samba Testsuite causes machine to crash

Dear all,
 
I decided to build Samba from source and have a look at the testsuite to
learn something about it.
So, after a configure (including the testsuite, see parameters below)
and a make, I tried
 
$ make quicktest # Which failed at some tests but left my virtual
machine running
 
and then
 
$ make test
 
For Samba 4.9.3 I noticed that running the full test suite lets my
virtual machine (1 CPU, 4GB RAM) crash right after
./st/simpleserver/smbd_test.log is written.
I tried the same with Samba 4.9.2 (because, you know, might be some of
that new stuff ^^) and it, too, crashes. This time right after
./st/nt4_dc_schannel/nmbd_test.log .
 
Short explanation how I got to these particular log files:
Since I did not find any central log of the testsuite, I did a `find`
for the most current .log file, assuming that whatever test wrote that
file made it to write the file to disk.
So either that test or the following test crashed the machine.
 
I will test the same thing with a VM with more RAM since I had a
somewhat similar issue (without the crash but with a failing build) with
another FOSS package recently.
 
Maybe someone can give me a hint. Thanks!
 
Bests,
Christian
 
 
========PS: My build sequence (both with 4.9.3 and 4.9.2):
 
./configure \
    --prefix=/usr \
    --enable-fhs \
    --sysconfdir=/etc \
    --localstatedir=/var \
    --with-privatedir=/var/lib/samba/private \
    --with-smbpasswd-file=/etc/samba/smbpasswd \
    --with-piddir=/var/run/samba \
    --with-pammodulesdir=/lib/x86_64-linux-gnu/security \
    --libdir=/usr/lib/x86_64-linux-gnu \
    --with-modulesdir=/usr/lib/x86_64-linux-gnu/samba \
    --datadir=/usr/share \
    --with-lockdir=/var/run/samba \
    --with-statedir=/var/lib/samba \
    --with-cachedir=/var/cache/samba \
    --with-socketpath=/var/run/ctdb/ctdbd.socket \
    --with-logdir=/var/log/ctdb \
    --systemd-install-services \
    --enable-selftest # This last option is needed for testing only
make
make quicktest
make test
 
=========PPS: Searching for the last log-file written.
cd samba-<version>
find ./ -name "*.log" -printf "%T@ %Tc %p\n" | sort -n
 
=========Host/VM/Guest:
 
Host: Windows 10
VM: VirtualBox 5.22
Guest: Ubuntu 18.04.1
VM RAM: 4 GB
VM CPU: 1
VM HDD: 20 GB
 
upgraded VM RAM: 8 GB
upgraded VM CPU: 2
upgraded VM HDD: 80 GB