Steps to reproduce:

1. Share some file with closed circle
2. Set share expiration date
3. Write some comment to recipients, press "send" arrow.
4. Reload page and check comments and expiration date - it's empty

Nextcloud 15.0.6, circles 0.16.3, Ubuntu 18.04, nginx1.14.0+php-fpm 7.3.4, MariaDB 10.1