We've been having this issue over at least one major upgrade where certain types of soft-credits just will not save, without leaving any type record in the error logs. Crediting an individual from another individual or organization works, but crediting an org or a household from an individual prevents the contribution from saving at all... if the soft-credit is removed the record will save fine. I took a video of what I mean and put it on YouTube here >> Video of soft-credit not saving
I have recently installed the Automatic Soft-credit extension Auto Soft-Credit Extension and it seems to bypass the issue, but there are many cases where I need to edit a contribution and cannot without deleting the soft-credit. Since we can't track payments toward an org or total household giving without soft-credits this leaves us with a serious issue.
Any ideas would be a great help. I am not a coder, but willing to use phpMyAdmin to look at the database or look into php code issues.
Thanks. We are on CiviCRM 4.6.22 and the latest Drupal 7 on a Debian 8 server with Apache.