Due to the nature of iOS, when the Send Anywhere app switches to background mode, the transfer stops. If you open another app or if the screen is locked when a file is being transferred, transfer stops.
To prevent transfer stop, Send Anywhere app is designed not to switch to background mode when sending and receiving files within our app. please be careful not to run other apps or lock the screen during the transfer.
(!) Note: When transferring files via SendAnywhere of iOS 
sharing, the screen may lock out depending on how long the device auto-lock setting. Please be careful not to turn off the screen until the transfer is completed.