It may be what Anssi says, I know support have had a number of reports that were for that reason.
Should SketchUp make the saving process really, really slow and introduce some complicated verification process to ensure that the file written has been saved correctly?
Many of these corrupt file cases are with older versions. Recent ones I’ve seen have been 2015 and 2016, but I’ve even seen v8 files. They all predate the more recent model verification overhead.