Ginger Gibson, Reuters Political Correspondent on the NPR show A1, was talking about Trump’s recent actions relative to the Roger Stone sentencing. This is a mashup of “teetering on the edge” (to be very close to a dangerous situation) and “walking a fine line” (in a dangerous situation where you could easily make a mistake). Both idioms involve dangerous situations, and “line” and “edge” are closely related. Not sure where “fragile” fits in, but “fine” has a similar meaning to “fragile”, to wit – fine means “having or requiring an intricate delicacy of touch” as in ‘delicate’, ‘fragile’, ‘frail’,” etc .” Here’s where you can hear a recording: at 7:25. https://the1a.org/segments/the-news-roundup-domestic-2020-014-02/
By the way, this is Ms. Gibson’s second malaphor. See https://malaphors.com/2018/05/18/the-buck-stops-at-the-top/.
A tip of the hat to David Barnes for hearing this one.