upgrade project from 5.4 to 5.5 and 5.6 giving Failed assemblies stripper.

My project was working fine when I was at Unity 5.4,

As soon as I upgrade my project to 5.5 It start giving me this error when I try to build apk, so couple of days back I upgraded it to 5.6.1f1 and well it is giving me same error at time of building. (BUILDING FOR ANDROID)

 Failed assemblies stripper: E:\Unity\Editor\Data\Mono\bin\mono.exe "E:\Unity\Editor\Data\Tools/UnusedBytecodeStripper.exe" -l none -c link -a "Assembly-CSharp-firstpass.dll" -a "Assembly-CSharp.dll" -a "Assembly-UnityScript-firstpass.dll" -a "Assembly-UnityScript.dll" -out output -x "E:\Unity\Editor\Data\Tools\link.xml" -d "Temp/StagingArea/Data/Managed" -x "tmplink.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\AI.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Animation.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Audio.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Cloth.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Core.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\CrashReporting.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\IMGUI.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Input.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\JSONSerialize.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\ParticlesLegacy.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\ParticleSystem.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\PerformanceReporting.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Physics.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Physics2D.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Terrain.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\TerrainPhysics.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\TextRendering.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UI.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UNET.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UnityAds.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UnityAnalytics.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UnityConnect.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UnityWebRequest.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\UnityWebRequestAudio.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Vehicles.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Video.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\VR.xml" -x "E:\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\Whitelists\Web.xml" current dir : Temp/StagingArea/Data/Managed
 result file exists: False. Timed out: False
 
 stdout:
 
 stderr:
 
 Unhandled Exception: Mono.Linker.ResolutionException: Can not resolve reference: UnityEngine.Vector2 UnityEngine.Vector2::SmoothDamp(UnityEngine.Vector2,UnityEngine.Vector2,UnityEngine.Vector2&,System.Single)
 
   at Mono.Linker.Steps.MarkStep.MarkMethod (Mono.Cecil.MethodReference reference, System.Object markedby) [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.MarkInstruction (Mono.Cecil.Cil.Instruction instruction, Mono.Cecil.MethodDefinition markedby) [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.MarkMethodBody (Mono.Cecil.Cil.MethodBody body) [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.ProcessMethod (Mono.Cecil.MethodDefinition method) [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.ProcessQueue () [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.Process () [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Steps.MarkStep.Process (Mono.Linker.LinkContext context) [0x00000] in <filename unknown>:0
 
   at Mono.Linker.Pipeline.Process (Mono.Linker.LinkContext context) [0x00000] in <filename unknown>:0
 
   at UnusedBytecodeStripper.Program.Main (System.String[] args) [0x00000] in <filename unknown>:0 

What I tried, Removed old plugins

No method in code uses Vector2.SmoothDamp

Tried to exlude Vector2.Smoothdamp from stripping https://docs.unity3d.com/Manual/iphone-playerSizeOptimization.html

Reimported ProjectS

Stripping set to OFF works but it increases apk size by 20mb which in turns make my overall apk size 100+mb. (Google play only allows upto 100mb size at a time without bundles) & its working with exact same settings in Unity 5.4

Please help in.

Its been 8 days I am stuck at this issue, my game is complete, just to use Splash Screen Tools, I upgraded my project and this happened.