Reproduction steps:
1) Download and open user's attached project (OwnCloud link and password are provided)
2) Build Scenes/GameStart.unity scene for Android platform
3) Run built project on several devices
-- Notice that some devices need 30 - 50 seconds to launch the game, while some are taking only 3 - 5 seconds

Reproduced with:
Unity 2017.3.0b11, 2017.3.0f3, 2018.1.5f1, 2018.3.0a2

Unable to reproduce with 2017.1.4p2, 2017.2.3p1, 2017.3.0b2,

Note: Issue is not reproducible when building for OpenGLES2 API

Devices under testing:
Unable to reproduce with:
Samsung Galaxy J5(2016) (SM-J510FN), Android: 6.0.1, CPU: Snapdragon 410 MSM8916, GPU: Adreno (TM) 306
LG G3 (LG-D855), Android: 5.0, CPU: Snapdragon 801 MSM8974AC, GPU: Adreno (TM) 330
Samsung Galaxy S6 (SM-G920F), Android: 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760
Samsung Galaxy S8 (SM-G950F), Android: 8.0.0, CPU: Exynos 9 Octa 8895, GPU: Mali-G71
Samsung Galaxy S9 (SM-G960F), Android: 8.0.0, CPU: Exynos 9 Series 9810, GPU: Mali-G72

Reproduced with:
Samsung Galaxy S9 (SM-G960U), Android: 8.0.0, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630
Google Pixel 2 XL (Pixel 2 XL), Android: 8.1.0, CPU: Snapdragon 835 MSM8998, GPU: Adreno (TM) 540
Google Pixel (Pixel), Android: 8.1.0, CPU: Snapdragon 821 MSM8996 Pro, GPU: Adreno (TM) 530
Huawei Nexus 6P (angler), Android: 8.0.0, CPU: Snapdragon 810 MSM8994, GPU: Adreno (TM) 430

By design: gpu instancing now produce a lot more shader variants, so preloading shaders will take longer on certain devices.