I pushed lightmaps from 1024 to 2048 resolution, is there any reason doing that would break the texture streaming?
Yes. If you have a lot of textures that are required to be streamed in and especially large lightmap resolutions with these it’s much more texture memory being used and may need more time to stream in or may not have a large enough streaming texture pool to draw from. Default is ~1gb for all textures.
Turning off streaming altogether does seem to solve the issue, but that’s probably not a good solution in the long run right?
For most, no this is definitely not a good solution! Texture streaming makes use of Mips to lower the resolution of the texture are further distances. When this is disabled the full resolution of the texture is continually loaded into memory rather than being lowered to make things more optimized. The suggestion was just a quick way to identify if that was in fact the issue you were running into.
If you’re goal here is a small scene to render and you have the hardware to handle a the large texture memory consumption then by all means do what works best for you. If you’re deploying this to lower-end hardware of need it to be deployed to different users or clients to run then optimization is best!