Rpi crashes on OpenCPN 4.8.4 charts

[CapnRon47]

I loaded Synaptic Package Manager and installed OpenCPN 4.8.4 on my Rpi 3. I have updated my charts (all RNC). I can scan the charts at a scale of 2.2 over a wide region, however under certain conditions (yet to be specified as they vary depending on chart scale, boundary, etc) the Rpi crashes. The crash is that I get a blank screen on the RPI I am currently running with a complete HDMI monitor, keyboard and mouse in place. I have to unplug and replug in the Rpi to reboot, no mouse click or keyboard entry shows anything. I looked at the OpenCPN logs and the log file just stops at that last point. The Rpi reboots with no indication of an error, the syslog and kernlog show nothing.

In its simplest form I start OpenCPN, I can zoom out to where I can see the border of my loaded charts. (scale 63600 1.9x) and here I can scroll around showing unloaded chart frames. I then zoom in to scale 122200 (3.5x) and start to scroll around and OpenCPN freezes and the RPi locks up. Other times it will crash the whole screen.

I don't know whether it is specifically an OpenCPN issue or a problem with my Rpi system. Just wondering if anyone has experienced anything similar.