Kerbal Space Program

When additional fuel tanks added to TwinBoar engine (except this engine is root part), these tanks has incorrect fuel priority (usually engine priority +10).
If engines uses in symmetry for aspsragus staging, all additional tanks has equal priority (max engine priority +10); this leads to an incorrect order of emptying the tanks.

HOW TO REPLICATE:
1. Make central core of rocket (for example, Mk1-3 Command Pod, Rockomax Jumbo-64 Fuel tank and "Mainsail" engine).
2. Set 4x symmetry mode.
3. Add 4 any radial decouplers to central core.
4. Place TwinBoar engines on decouplers.
5. Add any fuel tanks on these engines.

Expected: the tanks fuel priority equal to the priority of the engines.
Result/Observed: priority of tanks is 10 more (see screenshot 1).

6. Set staging to asparagus (move two of decouplers to new stage).

Expected: additional tanks fuel priority is different.
Result/Observed: priority of all additional tanks is equal (see screenshot 2).

Game version:
1.11.0.3045 (Windows Player x64) en-us, Steam (but it also happens in 1.10)
1.11.0 Making History
1.6.0 Breaking Ground
No any mods