The context is typically lost when the device goes to sleep and similar, and in most cases that recovers fine.
If you use the prefiltered cubemap for lighting, we have an issue with recovering it, and you should switch to a new type, which uses a 2D texture, which does not have this problem.
In the cubemap prefiltering dialog, delete the data first, and prefilter again, just don’t click on the "Generate legacy cubemap’.
