Flexed the loft part, and it just suddenly disappeared. Tried everything, nothing brings it back.
Your loft is a solid body; after the Flex feature it changes to a surface body, that does not seem right.
I try to never use the Flex and related tools, so I can't suggest what you might try to fix it. To troubleshoot, you might try flexing it just a little bit and then slowly increase the amount.
Another possibility is the base loft. Sketch1 should be defined (i.e. black instead of blue). Sketch2 is only a point. This works, but it is sometimes not best. You might try trimming the end of the "blade" off so that the geometry collapsing to a single point is removed.
If you look at the definition of the loft, an endpoint of sketch1 is going to the single point in sketch2. This can lead to a lot of unwanted twisting and other geometry defects.