Problem with 4.8.0.756 Update and Resco

I use the Obsolete Resco Mobile Forms Toolkit in my apps. After updating Xamarin to 4.8.0.756, my app crashes immediately on start up saying the app has had to close down. This happens of devices and emulators. The problem seems to be an unhandled exception (from Logcat):

03-03 16:30:42.375 2357 2357 I MonoDroid: java.lang.ClassNotFoundException: Di
dn't find class "md5d7aa2205d74d41f5ac48a297cf71ed7f.PopupDialog_ColorDrawableWi
thPadding" on path: DexPathList[[zip file "/data/app/Skylog.SkylogPro-1/base.apk
"],nativeLibraryDirectories=[/data/app/Skylog.SkylogPro-1/lib/x86, /data/app/Sky
log.SkylogPro-1/base.apk!/lib/x86, /vendor/lib, /system/lib]]

Reverting to Xamarin 4.2.0.695 fixes the problem. Since Resco don't support their product any more, can Xamarin provide a fix? Otherwise, I'm stuck at this version.

Using VS 2015 with Java jdk1.8.0_102.

Thanks...Andrew