Thanks for your inquiry.
There are several text replacement issues, which have already been logged in our issue tracking system. However, they all are different in nature and scenario specific. We have already improved our text replacement engine and have been working over improving it more, in every release of the API.
In most of the basic scenarios of text replacements, where no font size change is required, the API does not raise any issue and produces correct result. Whereas, in your specific scenario, the font size of new text is being changed in code and causing the issue in output file.
Since, the issue is reported and logged under free support model, it has low priority and will be investigated on first come first serve basis. There is already a long queue of pending issues, which were logged prior to your issue. Therefore, we will definitely inform you as soon as we make some significant progress towards issue rectification.
Furthermore, we also offer paid support model where issues are resolved on urgent basis and have high priority. You may also check our paid support and its policies over our website.