If it happens after a day or so, memory is certainly a factor. Also, https://bugzil.la/695693 https://bugzil.la/695693 might be relevant, one of the comments e

If it happens after a day or so, memory is certainly a factor. Also, https://bugzil.la/695693 https://bugzil.la/695693 might be relevant, one of the comments explains how to diagnose if this is a reflow bug.