This is already known, see here: ✏ Android 7 update: most annoying bugs, FAQ, etc
As far as I know the fix is supposed to come with the next update: https://bugtracker.fairphone.com/project/fairphone-android-7/issue/26
In case you are familiar with flashing software with fastboot you could already fix it now by flashing aboot (take it from the manual install files)
fastboot flash examples when you downloaded the manual install ZIP
On Windows:
fastboot.exe flash aboot images\emmc_appsboot.mbn from the extracted archive directory.
On *NIX (GNU/Linux and macOS):
fastboot flash aboot images/emmc_appsboot.mbn , again from within the extracted archive directory.