Best way to deal with Lighting Build running out of memory?

Yeah, that’s whats confusing me. It’s definitely running out of memory. See attachment.

Im trying to get some decent shadows. I dont think it’s that high given that each wall object object has about 100m2 of flat surface. Correct me if I’m wrong. Using 4.6.1…

On another note, it takes longer to crash when I turn the direct light & enviornment light to “Stationary” as opposed to “Static”. Any difference in quality there? Given they are static, I thought static would have been the best option…?

Cheers