Material corresponding to this chapter appears twice in the bamboo slip manuscripts recovered in 1993 from a tomb at Guodian, in Hubei, and the two occurrences are not in the same bundle and do not read identically. That makes chapter sixty-four one of the most useful passages in the book for anyone asking what kind of text this is.
The Guodian slips are the oldest witnesses to this material known, from a tomb dated to around the end of the fourth century before the common era. They contain roughly a third of what the received text has, distributed across separate bundles, with no division into a Dao part and a De part and nothing corresponding to the eighty-one chapters.
Finding the same passage in two bundles, with variation between them, tells against the picture of a single book being copied and tells for a picture of circulating units of material that different collections drew on. The received chapter is then a compilation of such units, and the differences between the two Guodian versions are not errors by a careless scribe but evidence that more than one version was in use at once.
That does not make the received text unreliable. It makes it what it is: a late and remarkably stable arrangement of older material, and the stability is real, since what the slips contain is recognisably the same sayings.
It does mean that questions about the original wording of a line are often the wrong questions, because for some passages there may never have been a single original wording to recover.