отстающий(We are behind the curve when it comes to advances in medicine. [=we have not been keeping up with the latest advances as well as others]vogeler)
отставать(We are behind the curve when it comes to advances in medicine. [=we have not been keeping up with the latest advances as well as others]vogeler)
подкинуть неприятный сюрприз(informal: Unexpectedly present someone with a challenge or disruption: ‘just when you think things are working out, life throws you a curveball' Bullfinch)