Steps to reproduce:
1. Open User-supplied project ("testSpecBug.zip")
2. Build and run the "test" scene
3. Inspect the white specular highlight in the middle

Expected: the light is smooth.
Actual: the light's edges are hard and of low quality.

Reproduced in: 2019.1.10f1 2019.2.0b10
Not reproduced in: 2017.4.30f1*, 2018.4.4f1*, 2019.3.0a9*

Note:
*Could not test due to all textures breaking.

Not reproducible in Editor.
Converting to HDRP completely breaks all the textures, upgrading project materials to High definition materials does not fix this issue.
Not reproducible on Windows Standalone.
Reproduces on iPhone 7 Plus iOS 12.0, the red texture turn instantly to white at around size 300.
Added a screenshot from Meizu - (MX5).

Tested Devices:
Repro: VLNQA00005, Samsung Galaxy S7 (SM-G930V), Android 7.0, CPU: Snapdragon 820 MSM8996, GPU: Adreno (TM) 530
Repro: VLNQA00004, Meizu - (MX5), Android 5.0.1, CPU: MediaTek Helio X10 MT6795T, GPU: PowerVR Rogue G6200
Repro: VLNQA00057, Htc One M9+ (HTC_M9pw), Android 5.0.2, CPU: MediaTek Helio X10 MT6795T, GPU: PowerVR Rogue G6200

VLNQA00165, Samsung Galaxy S7 (SM-G930F), Android 7.0, CPU: Exynos 8 Octa 8890, GPU: Mali-T880
Everything is fine at first, but the whole render disappears on around 2.4k size.