Do you have Visual Studio 2015 installed? The VS 2015 Redistributes are required for Lightmass building in 4.10. Please update to VS 2015 or install the 2015 Redistribute (located below) and let me know if this fixes the error you are seeing. If not, please post this to the answerhub in the bug reports section (link in signature) so I can assist you more in depth.
Edit: The specific Redistribute needed can be found here if you do not have VS 2015 installed. If you have 2015 installed, do not install this redistribute.
Is 4.10 preview loading very slow for someone else too? Getting ~2x loadtime. Thought my 16gb ram just wasnt enough (was constantly reaching full memory use), but now after installing win10 (and getting 24gb) its still very slow to load. I have 12000 actors, around 1-2million foliage meshes and 2x2km^2 map. Just to compare. Else superb engine and nice to see so many updates, cant stop being over excited.
Is there a place where we can see a backlog of issues that haven’t been addressed? It’d be nice to have a look at a list of issues (in something like Jira) and pick some that the UE dev team won’t get around to.
During the game jam I got A LOT of crashing in Blueprints by using Ctrl-Z regularly. I considered looking into it but I have no idea if it’s something being worked on and if so where it’s at.