combine two gears does not work with double helix gears

[kes31]

Freecad version 0.20.2 Plugin version: master

Steps for reproduction:

• create an involute gear, set teeth to 30, beta to 20 and enable double_helix
• create a second involute gear, keep teeth at 15, set beta to -20 and enable double_helix
• select both gears and use combine two gears

Found result:

• position of gears is not correct and error is found "InvoluteGear001 still touched after recompute"