Publisize/scheduled post custom message not saving

Hello all,

I tried to use the publicize feature for the first time earlier, after resolving a bug with my website. I added Facebook and Twitter, filled in the custom message and upon hitting publish, this worked fine.

However, when I scheduled a post instead, I noticed that the custom message would not save.

This problem seems to have surfaced elsewhere: https://github.com/Automattic/jetpack/issues/1586

The video link contained within shows my problem exactly:
http://d.pr/v/18GoG

I have tried this on different posts, but to no avail. I have the latest version of WordPress.

Any help would be greatly appreciated, as this is the final hurdle now with the issues on my site.

Kind regards,
IRI5HJ4CK.

https://wordpress.org/plugins/jetpack/