Nothing new yet, but another source:
https://www.marketwatch.com/story/pence-called-back-to-washington-from-new-hampshire-trip-reports-2019-07-02?link=sfmw_tw
“A spokesperson for the vice president originally said Air Force 2 was turned around due to an “emergency” but a spokesperson for the organizers of the New Hampshire event has since clarified that it was a “diversion” and not an emergency.
No further information was immediately available.”