I have a lot of assetbunlde files (more than 200) builded with unity 5.4.1 , old version app on IOS platform also is builded with unity 5.4.1, so can load those assetbundle and create objects successfully. Now the app update with new version unity 2017.3.1 , it also can load those old version assetbunlde files, but all of objects from loaded bundle lost their shader(most of materials with unity stand shader , others with custom shader ), whole object become pink color.
how to fix this issue? except rebuild assetbundle with unity 2017.3.1, it will spend a lot of time.
on IOS platform, does asset bundle has backward compatibility to unity?
need your help , thanks a lot !
I’m afraid rebuilding asset bundles is the only option for you. Unity can load bundles built using older versions, but there are no guarantees about full backward compatibility. Shaders in particular are not very compatible across releases and in your case specifically you are upgrading 3 Unity releases forward, so compatibility issues are very likely.
got it . thank you very much
I got the same issue. what was the solution? all my custome shaders not working anymore. why does unity do stuff like this in a newer version 
I decide to rebuild my asset bundle files with newer unity version , no better method. : (