I posted way back when Seblod was 3.1.5 and I figured this bug would of been fixed by now with the latest version, But it isn't and it totally shuts down my clients sites. When will this notorious issue be fixed.
Today it happened when I simply went into Components -> Seblod 3.x -> Lists & Search Types -> Clicked my own I created -> The "Item" tab and "Field Tab" was selected by default -> and I simply added a field to Mainbody and clicked Save. That should not break the template. I didn't unselect the template. This makes it almost impossible to continue making custom changes if its going to produce "Error Oops! Template not found.." error on front end. There are so many complaints about this.
I really think you are on to something. The bug goes like this. By default positions like header, footer, left are set to 0 meaning off. Most, if not all of use usually uses one or all of those positions so we turn them on and then add the fields to those positions. What happens is that sometimes (and there is no pattern) when you go to edit a Content Type, the positions "RESET" back to the default 0 (off) . Which breaks the template.
The solution in plain terms is to make sure SEBLOD "loads" the saved settings the user has done all the time. It seems like it preloads the defaults then updates the settings to what we use, but doesn't always work.
it is not my call to include this in next release, but having few good test will certainly help. Chaged fiels are tempalte layouts so to test without hacking core files you can easily create template overrides in your admin template