If you haven't already considered mbsync as an alternative to OfflineIMAP, I suggest taking a look. I also found OfflineIMAP buggy (many years ago) and mbsync has been syncing my mailboxes reliably since. http://isync.sourceforge.net/
I say this as the author of a program that runs mailbox syncers like mbsync when there are changes to sync (mswatch: http://mswatch.sourceforge.net/).
You might try a similar program, mbsync (http://isync.sourceforge.net/). It's worked well for me during the past half-dozen years.
mbsync does not watch or poll for changes, but you can run mbsync in a loop from your shell. Or, if you are running Linux on the mail server and client and use Maildirs, you can run mbsync from mswatch (http://mswatch.sourceforge.net/). (Disclaimer: I'm the author of mswatch.)
If the overhead of a subversion checkout storing each file twice is too much for your dataset and drive, you might take a look using scord with subversion, which allows your checkout to store only one copy of each unmodified file. http://scord.sourceforge.net/
A little more detail: In addition to the working copy of a file, a subversion checkout includes a pristine version of each file for diffing (e.g., 'svn diff', as well as to make 'svn update' and 'svn commit' more efficient). scord is a Linux and Mac OS X FUSE file system that mediates access to a directory tree, detects when a pristine and working copy pair contain the same content, and keeps only one copy around in these cases.
I store my photo album in subversion - I love not having to worry about accidentally losing a photo. Halving the disk space needed for the checkout lets me fit my photo album into my laptop harddrive.