I go for option 4.

FYI, here’s what I wrote in my blog when the Shipton photos were recently sold. I recounted in more detail in my book Shadows of Existence my uncomfortable efforts to produce something resembling the Shipton tracks in snow by a comination of barefoot parints and those made with various types of footwear, in different textures of snow, under different time/sunlight conditions. This “overprint” explanation, which Napier sort of tentatively offered, never works: it doesn’t even come close. (Meldrum says the same thing, but what’s funny is I have yet to read of anybody except me actually trying the experiment.)

BLOG ENTRY:
While the evidence for the yeti is unsatisfying at best, no one has ever explained these footprints. Options:
1. An unknown animal.
2. Prints of known animals (or humans) expanded by melting and refreezing. This is easy enough to disprove experimentally. Tracks melt into a blob - they don’t expand in a way that gives you clear edges and well-defined toes.
3. A hoax. No evidence Shipton and his companion Ward hoaxed the prints has ever been offered.
4. Simply, a mystery.