WEBENCH® Tools/LM2586: Dimensioning and efficiency for multi-rail output

Tool/software: WEBENCH® Design Tools

Team,

my customer needs advice for dimentioning a design with LM2586

What they have:
My customer is using LM2586-ADJ in an older project to generate +/-13V. I have attached a schematic at the bottom of this post.
The circuit was designed and dimensioned using Webench and the following specification:

• Vin: 9V-30V
• Vout: +/-13V with 25mA each

The transformer recommended in the datasheet could not be used due to height restraints in the design. They are using Epcos B1032.
The circuit works, but has bad efficiency of approx. 40%.

What the need for a new project:
The new project has higher output current requirements for the +13V rail -> 50mA.

@Vin=24V, there is no problem.
When Vin is dropping to <15V, the LM2586 draws extraordinary high current, such as 400mA @10V.
That means efficiency is very bad and at sime point, the transformer just burns.

Webench:
The first design was done a few years ago and today, Webench does not allow multi-output designs for LM2586.

Questions

• Can you advise how to dimension for their new requirements?
• Do you know why Webench cannot run the simulation anymore?

Thanks for your support!

Schematic for "old" design: