再三 + Verb (over and over)

Checked it, checked it again

• over and over again再三zài sān = "over and over / repeatedly / again and again".
• over and over again再三zài sānto think over考虑kǎo lǜ = "think it over and over."
• It stresses an action done insistently, several times.

over and over again再三zài sān + Verb

• over and over again再三zài sān marks a repeated, earnest action (usually two-syllable verbs).

he他tārepeatedly再三zài sānstress强调qiáng diàothis这zhèpoint一点yì diǎn。

• over and over again再三zài sānto emphasize (a statement)强调qiáng diào = "stressed (it) over and over."

Recap

Read the full reference: HSK 5 grammar — Adverbs.