差点没 + Verb (almost didn't)

The double negative that isn't

• almost差点chà diǎnnot / haven't没méi + Verb is a tricky cousin of almost差点chà diǎn.
• With a wanted result: almost差点chà diǎnnot / haven't没méito keep up with赶上gǎn shàng = "almost missed it (but caught it)."
• With an unwanted one: almost差点chà diǎnnot / haven't没méito fall down摔倒shuāi dǎo = "almost fell" (= almost差点chà diǎnto fall down摔倒shuāi dǎo).

Subj + almost差点chà diǎnnot / haven't没méi + Verb

• The not / haven't没méi is often "empty" — the meaning depends on whether the result is wanted.

I我wǒalmost (didn't)差点没chà diǎn méicatch赶上gǎn shàngbus车chē。

• almost差点chà diǎnnot / haven't没méito keep up with赶上gǎn shàngwar chariot (archaic)车chē = "I almost missed the bus (but made it)."

Recap

Read the full reference: HSK 5 grammar — Adverbs.