Annually-recurring hairline sheetrock ceiling cracks

[mac]

I've filled and painted; they return. Is a sand and re-tape - maybe with fiberglass tape - the only real option?
Since this also acts as a vapor barrier - is it something I would even need to worry about? These cracks close and become invisible in summer.
Thanks,
Mac

[mac]

Further research shows these to be cosmetic, in most builders' eyes (site-built and other). The foundation is fine, it's a slab. I'll try forcing filler in, and painting, and see what happens.