For some reason after exporting the new April release schemas myself, deleting the UIGenTestModelparse.schema and running the Serializer through CMD as admin. (Windows 7 pro) The process finishes with no error but does not produce a new dll in my C:\toolset folder or anywhere for that matter. My guess is that the latest ST patch added new schemas that will have to be edited.
Well, for starters, it appears they changed the window title of the client (again), which means it is not recognized by ExportSchemas, and thus, you cannot export the game client (as opposed to launcher) schemas to rebuild a new serializer library. That requires editing the toolkit source, and recompiling, which I've now done.
After that, I generated a new serialization library using schemas from the current client version and (with the additional change to the parser hash value I mentioned) GenerateResource -x now processes CostumeGeometryClient.bin without complaint (it is very slow - maybe because a large number of xml files are generated - but no errors). I can also then run GenerateResource -b on the results, and I get a new CostumeGeometryClient.bin file with the same length as the original. I put it into my Live\localdata\bin folder, and it didn't crash the client, so basic sanity checks seem to pass.
Thus, (fingers crossed) maybe this new version of the toolset will now work with that file.
I attach the updated toolset, including the new schemas, serializer and modified .json file. As before, I recommend deleting any old xml files and re-running GenerateResource -x with the new toolset, as xml generated from the previous version may not be compatible.