Select dynamic cascade retrieves values with ajax, so if something is not ok with ajax response it can mess the selects. If not already, you will need to update seblod and all extensions like select dynamic cascade
Updating the dynamic cascade field helped me solving this issue. The problem is that neither SEBLOD nor its plugins use the Joomla update process. Hence nobody knows when updates are available unless one checks constantly manually which of course with 30 plugins installed is almost impossible. Therefore I urge the SEBLOD team to come up with a reliable update process, thanks.