Do you have a large video background library, maybe many 4k clips or 1 really big one?
FYI, 5GB of Ram is nothing, try 22GB 
which I achieved in testing.
Is your laptop freezing when it approaches 95%-97% ram utilization ?
It wouldn’t be strange, since it’s trying to use the swap on your storage (ssd / hdd).
So here are the (potential) solution! There are 3 options:
- downgrade
- rename the ./quelea/vid to something else like ./quelea/vid(diabled) or just ./quelea/vid(i am so sad). After doing that you should be using somewhere between 700Mb to 1100Mb but not more really.
- uninstall quelea and else , like OpenLP (sometimes, that’s the reality)
Let’s hope for the best!