@davidmead I'm curious what method you're using for syndicating to twitter that's causing this? That may be the better question to address. It's likely if you're having a problem, others will as well.
In the interim, you can find all the prior releases here: https://github.com/pfefferle/SemPress/releases. From here you also have the ability to view the changes between releases so you can potentially easily track down the pieces of code which changed and may be causing issues.
You might also find it easier to create a [child theme](http://indieweb.org/WordPress/Themes#Child_Themes) of SemPress with some small changes to improve your specific issues, this way you'll still get other future updates from the parent.