Steps to reproduce:
1. Open project from OC link
2. Build for Android
3. Observe the shadow quality being significantly worse on mentioned Unity versions

Expected: Shadow quality remains the same throughout different Unity versions
Actual: Current stable versions have shadow quality degraded

Reproduced on: 5.6.5f1, 2017.1.3f1, 2017.2.1p1, 2017.3.0p1
No repro: 5.5.6f1, 2018.1.0b1

Devices Under Test:
Repro:
Amazon KFFOWI (Fire (2015)), OS:5.1.1, CPU:armeabi-v7a, GPU:Mali-450 MP, Build:Amazon/full_ford/ford:5.1.1/LMY47O/37.5.4.2_user_542169020:user/release-keys

(Shadows wouldn't load at all)
Samsung GT S5310, OS:4.1.2, CPU:armeabi-v7a, GPU:VideoCore IV HW, Build:samsung/corsicassxx/corsicass:4.1.2/JZO54K/S5310XXAME2:user/release-keys

(Project wouldn't load) (brokescreen.png) (SEPARATE ISSUE, FIXED ON 2018.1.0b1)
Google Nexus 7, OS:5.1.1, CPU:armeabi-v7a, GPU:NVIDIA Tegra 3, Build:google/nakasi/grouper:5.1.1/LMY47V/1836172:user/release-keys

No Repro:
Amazon KFMEWI (Fire HD 8 (2015)), OS:5.1.1, CPU:armeabi-v7a, GPU:PowerVR Rogue G6200, Build:Amazon/full_thebes/thebes:5.1.1/LVY48F/32.5.6.0_user_560177220:user/release-keys
Amazon KFTBWI (Kindle Fire HD 10 (2015)), OS:5.1.1, CPU:armeabi-v7a, GPU:PowerVR Rogue G6200, Build:Amazon/full_thebes/thebes:5.1.1/LVY48F/32.5.9.5_user_595457220:user/release-keys
Google Pixel C, OS:7.1.1, CPU:arm64-v8a, GPU:NVIDIA Tegra, Build:google/ryu/dragon:7.1.1/N4F26O/3582057:user/release-keys
Amazon KFSAWA, OS:5.1.1, CPU:armeabi-v7a, GPU:Adreno (TM) 420, Build:Amazon/saturn/saturn:5.1.1/LVY48F/22.5.7.9_user_579225620:user/release-keys
Samsung SGH T999, OS:4.3, CPU:armeabi-v7a, GPU:Adreno (TM) 225, Build:samsung/d2tmo/d2tmo:4.3/JSS15J/T999UVUEOH1:user/release-keys
Samsung SM G930F, OS:7.0, CPU:arm64-v8a, GPU:Mali-T880, Build:samsung/heroltexx/herolte:7.0/NRD90M/G930FXXU1DQJ3:user/release-keys
Asus K011, OS:4.4.2, CPU:x86, GPU:Intel/BayTrail, Build:asus/WW_K011/K011:4.4.2/KOT49H/WW_user_3.1.23.191_20160107:user/release-keys
Samsung SM G950F*, OS:7.0, CPU:arm64-v8a, GPU:Mali-G71, Build:samsung/dreamltexx/dreamlte:7.0/NRD90M/G950FXXU1AQH3:user/release-keys

Notes: on 2018.1 it seems the distance fall-off is a mix between how it worked in 5.5 and 2017.3 - the shadow fades away, but at the same time is rendered fully, hence the split in the picture