Possible race conditions when compiling and running

I'm seeing this in logs for `/compile` requests:

A web handler threw an exception. Details:
data/haskell/build/Pxx/Pxxxxxxxxxxxxxxxxxxxxxx.basever: openFile: does not exist (No such file or directory)

This indicates that some part of the system thinks the build is done, but there's no basever file. I'm not sure how that could happen. Maybe a race condition of some kind?

I also see this for `/runMsg`:

A web handler threw an exception. Details:
data/haskell/build/Pxx/Pxxxxxxxxxxxxxxxxxxxxxx.err.txt: getFileStatus: does not exist (No such file or directory)

Similar situation: the system thinks that the build is complete, but there's no build output file, which should always be created as part of a build.