Bug or documentation error? Base Design

[RogalDorn]

I tried to simply post images of the rulebook and design log but due to the wonders of arbitrary forum requirements I'm not allowed to.

The Structural Design Score is randomized with the first version of a Model
and will not change with subsequent versions

My light tank Mk Is have 98 structural design. My Mk IIs have 87. I used the upgrade model, not new model option of course. Additionally, both models have identical attack stats despite significant field testing (65% completed) and this blurb

The way to improve this Basic Design Score is through Field Testing. Or in
other words getting your Models produced and tested in real battle.
The Structural Design Score and Basic Design Score impacts the Engine
Design, Weapon Design and Armor Design Stats. These are also randomized
with the first version of a New Model, but they’ll (probably) improve with
each new version of of the Model (irrespective of Field Testing).

which states it should increase.
Am I misinterpreting something?
Is the manual wrong?
Is there a bug?

[Destragon]

When you click on one of your models, there's an "open design log" button in the bottom right that gives you more insight into how the numbers came to be. It has to do with random die rolls, so improvement is not guaranteed.
However, structural design is not supposed to change after redesigning a model. If that happened, it sounds like a bug. What version was that on?

[RogalDorn]

I had to use that screen to find the values I give. Version 1.03, no beta patches.

[Jdane]

In my understanding Field Testing improves Base Design, not Structural Design.
But mark IIs shouldn't end up having a lower Structural Design than the mark Is.
And your software is up to date.
I'm as puzzled as you are. [&:]
(And agree those forums requirements are a bit of pain as for information sharing is concerned. A screen capture of the models' design stats from under MNG could have been of some help here.)

[Culthrasa]

In 1.03 some bug remain in the design process... If you switch to the latest beta all will be sorted. (beta1 and beta2 fixed it...)

[Vhalor]

Structural design indeed will change with each updated model design. Has no impact though, as the original Structural design always overwrites at the end.

Also, stats do not have to rise just because field testing raised basic design. It only increases the chance for weapon / armor / engine design to increase. But if those are high already, it's quite likely that nothing at all will be improved.