Since upgrading to OS X 10.10 Yosemite, the problem following a contraction has appeared. Also, if there are two letters following the apostrophe, the second letter floats to the end of the next word.
Not reproducible on osx 10.10 with Version: 4.4.0.0.alpha1+ Build ID: 4dbed9ef9a2299587d75bd9fae96b05dac0675c3
Not reproducible on Version: 4.3.3.1 Build ID: 7d55112667c8fcddb67bc3803796b46c93aa56b0 setting as wfm