From that log it seems the project got corrupted somehow … Either there could be a defective hardware issue (RAM, SSD/HDU usually are the culprit but it might be the motherboard too) a hardware driver issue or it is a critical UE4 bug leading to corruption. I would first check the hardware to ensure everything is fine using SSD/HDU manufacturer low level sector-by-sector scanning utils and MemTest86 or MemTest86+ to check the RAM (which ensures CPU with its internal caches is working properly too). If the system is overclocked testing the hardware is obviously needed even more. Then if any driver was updated testing that would require more time and reinstalling the OS could be needed too (having boot OS partition backup images would save time, it is way faster restoring and checking than starting from scratch). If all tests would end up being good then you could send the corrupted project to Epic Games along with all the UE4 logs because it might be a serious bug needing them to fix it ASAP.