hi @Stew ,
This is a complex problem, and there are many different reasons for this problem.
You situation where all you project fail is something more unique.
There was a past post, which is a very descriptive possible answer
Memory Calculation - Editor keeps disconnecting - General / Issues and Bug Reporting
The other thing to do is verify your installation, due to many project failures
Verify your UEFN installation
When there is a single project, causing problems, it’s usually an asset, like Landscape, which is causing problems.
Check that your memory usage is 75% or less, about 75 KB, find a project with low usage and test with that.
Check the local memory size list of sizes, and check for any really large custom assets more than 10%