In Suetonius' "Div. Aug. 28.2":
"...et moriens ut feram mecum spem mansura in vestigio suo fundamenta rei publicae quae iecero." =
"...and in dying I will carry the hope with me, that the foundations which I have laid for its future government will stand firm and stable." (Perseus: Alexander Thomson, 1889)
In John-Buchan's book, "Augustus", p.129:
"...and bear with me the hope when I die that the foundations that I have laid will remain unshaken."
The neuter noun, "vestigium", has its well-known definitions: "footprint"; "track"; "sole-of-foot"; "imprint"; "vestige"; in the ablative, "e vestigio" = "immediately" (Oxford; L&S). The translations of "vestigio suo" = "firm"; "stable"; "unshaken", above, do not appear to fit with any of these established ones; apart from, "in its foot", which sounds fatuous.
What's going on, here?