To crop up is to appear unexpectedly. Something has cropped up.
Saying something has come to crop up is the standard polite excuse, and everybody understands it as one. A problem that continues to crop up is a pattern rather than an accident.
1phrasecrop upTo appear unexpectedly.
“The same question will crop up at every meeting until it is answered.”
crop up is a phrase.
Practised in Phrasal Verbs