After upgrading to a new machine i9-14900KF 24 core, rtx 4090 24gb. unreal (any version of 5 upto 5.4.2) where either extremely unstable with random crashes. also opening projects would crash before load.
there is a problem with unreal and the latest gen processors and it appears to be memory leaks due to the access violation.
Solution!
For intel i9 download Intel(R) Extreme Tuning Utility, change the performance core ratio from 57x (was my default) to 53x, apply and run unreal. it should now work.
This is just a hack untill hopefully unreal engine patches this problem.
NOTE: you need to change this everytime you reboot as it resets to its default.
Let me know if it works for you?