Siri controls my HomeKit Meross smart plugs incorrectly

Dear community,

I use a Meross MSS425F smart plug (4 power outlets in one device - let's call them A1, A2, A3, A4 to explain my problem) and four single-power plugs Meross MSS210 (Let's call them outlets B, C, D, E).

I have grouped these outlets and combined outlets from the MSS425F with single-plugs like this:

Group 1 = A1+B

Group 2 = A2+A3+A4+C

It works perfectly to operate these groups in the HOME App on the iPhone. If I click on Group 1 then A1 and B turn on, etc.

But, if I use Siri voice control and say "Hey Siri, turn Group 1 on" then something unexpected happens: All A-plugs (A1, A2, A3, A4) would turn on and also B. Same with Group 2.

So obviously Siri tells the whole 4-plug-device MSS425 to turn on even though it should not.

Firmware is all up to date. I already bought a new MSS425 and reconfigured everything from scratch. I reseted everything and tried the usual hints. Nothing would work.

Any ideas how to fix this?

Thank you!

Best regards,

Christian