Thunderbird formatting emails with odd tabs upon sending / saving as drafts

Question

We use Thunderbird as the desktop mail client on a couple of machines, the actual emails server is gmail (Google apps for business) we connect via imap.

The problem we are having is sometimes when sending an email (or saving it as a draft) it will sometimes start to break the sentences really oddly.

For instance if i had the paragraph below

It would become broken like this

See that it keeps the first word of each paragraph, then drops the rest and indents it. Any idea why it does this and what can be done to stop it occurring ?

This is in Thunderbird 17.0.8 on OSX while composing html emails