To reproduce:
1. Open users attached project "SyncLoadBundleStall.zip"
2. Build for iOS
3. Deploy the Xcode project to an iOS device
4. Press "Load Level" button

Expected results: another scene is loaded instantly and yellow pulsing shader can be seen
Actual results: it takes a considerable amount of time to load the scene

Reproduced on:
2017.4.0f1 2018.3.2f1 2019.1.0a7

Not reproduced on:
2019.1.0a8 2019.2.0a1

Devices reproduced on:
iPhone 7 Plus iOS 11.1.1
iPhone 6 iOS 10.3.3

Devices not reproduced on:
iPhone XS Max iOS 12.0
iPhone 8 Plus iOS 11.0

Notes:
On 2017.4.0f1 on the devices that the issue was reproduced the time between the scene switches is a lot lower than on 2018.3.2f1