Hello. Thank you for contacting the Toolset support.
Well - could you please tell me how and where you are using the custom shortcode you wrote.
It looks like field _sale_price_dates_to stores unix timestamp but I can guide you in right direction if you can share problem URL and access details with me.
*** Please make a FULL BACKUP of your database and website.***
I would also eventually need to request temporary access (WP-Admin and FTP) to your site. Preferably to a test site where the problem has been replicated if possible in order to be of better help and check if some configurations might need to be changed.
I would additionally need your permission to de- and re-activate Plugins and the Theme, and to change configurations on the site. This is also a reason the backup is really important. If you agree to this, please use the form fields I have enabled below to provide temporary access details (wp-admin and FTP).
I have set the next reply to private which means only you and I have access to it.