Due to the nature of iOS, transfers are paused when the Send Anywhere app switches to background mode for security reasons.
Please do not launch other apps or lock your device during the transfer until the transfer is complete.
In SendAnywhere app
To prevent transfer stops, Send Anywhere app is designed to stay active and not switch to background mode when transferring files. Please avoid opening other apps or locking the screen during the transfer.
In other apps, such as the Photos or Files app
If you tap 
Share button in other apps and then select Send Anywhere to transfer files, your screen may go into a locked state depending on your device's lock settings. If your screen gets locked, the transfer will be immediately canceled. Please be careful not to turn off the screen until the transfer is complete.