Terms for subject Idiomatic containing звоночек

Russian	English
первый звоночек	a shot across the bow (Оли Гогелиа)
прозвенел тревожный звоночек	alarm bells went off (alarm bells go off / ring / sound (Cambridge Dictionary): Через несколько месяцев прозвенел новый тревожный звоночек. Жителей всполошила фраза, брошенная работниками водоканала... (из рус. источников) • Alarm bells went off in the industry when the law was proposed. (Cambridge Dictionary) ART Vancouver)
стать тревожным "звоночком"	raise red flags (4uzhoj)
тревожный звоночек	red flag (There is always a chance that unforeseeable circumstances happen, which can cause rescheduling and longer response times, but if this is happening consistently, it should be a red flag and taken with great caution moving forward. 4uzhoj)