Hi Nikolay,
Can you provide your material setup for this blendable. In the examples I have from 4.10 - 4.12 I see the same results.
I see several JIRA’s entered regarding Blend Weights, so it may be possible on of these has already been reported, but just want to confirm first.
Also, can you try your blendable on 4.12 Preview 5 that is available in the Epic Games Launcher to verify this hasn’t already been fixed.
Thank you!
Tim