I haven’t had great luck with W.P. Landscape HLODs either.
I have tried up to 5.2.1, and I usually get memory errors on my 128GB system.
I originally tried creating HLODs on large heightmaps on my R9-5950X 16C/32T, ASUS ROG X570, 128GB DDR4, ASUS TUF RTX-3080.
I have a new workstation now that I will be trying it on which should not have any memory problems any more: Intel W7-2495X 24C/48T, ASUS Pro W790 ACE, 512GB DDR5 ECC, ASUS ROG STRIX RTX-3090.
I will see if UE5 has other issues still with this much memory on some tests here shortly.
Note: Page File size almost never fixes every malloc issue, especially if the Page File has to be significantly larger than the RAM memory.