Mismatched serialization in the builtin class 'Transform'

Hi all, been writing and testing my game on Linux, just made a windows build to try out on there and it builds successfully, but fails on the main menu (first scene) with these sorts of errors in the log file:

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Mismatched serialization in the builtin class 'Transform'

(Filename: C:\buildslave\unity\build\Runtime/Serialize/SerializedFile.cpp Line: 1912)
Mismatched serialization in the builtin class 'Transform'. (Read 15 bytes but expected 68 bytes)

(Filename: C:\buildslave\unity\build\Runtime/Serialize/SerializedFile.cpp Line: 1912)
<blah>..._Data/level0' is corrupted! Remove it and launch unity again!
[Position out of bounds!]

(Filename: C:\buildslave\unity\build\Runtime/Serialize/SerializedFile.cpp Line: 1905)
A script behaviour (probably ?) has a different serialization layout when loading. (Read 15 bytes but expected 288 bytes)
Did you #ifdef UNITY_EDITOR a section of your serialized properties in any of your scripts?
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I do not have any #ifdef in my project code.
Using Linux Editor 2017.3.0b1

seems like similar problems in Unity 4 (2013), but can't find any recent issues like this.
I did try selecting Assets and choosing "Reimport all" - no effect.
This is a local build, going to try a cloud build next, but this is very disconcerting that everything runs in Linux Editor and Linux standalone Player just fine, also tried Android Player, also fine. Windows will naturally be the most popular target platform...so...HELP!

UPDATE: I've reverted back to a non-beta version and all is well. I'll avoid using betas for production from now on Rookie mistake. *blushes*