System: Intel Core i3 8100 processor, GIGABYTE H310M-H UEFI Motherboard, Windows 10 on SSD.
Events sequence: I installed Ubuntu (18.04 LTS) on my Windows 10 PC, on a HDD. Windows is on SSD. Ubuntu identified SSD as sdc and HDD as sda. Didn't want GRUB to take over, so I recovered windows bootloader and the system started directly logging into windows. Then I installed EasyBCD, added a GRUB2 entry for Ubuntu with "Automatically detect and load" drive option. Finally I selected "Use Metro bootloader" and saved the settings. The PC shows options for Windows 10 and Ubuntu at startup on a windows style screen. So far so good.
Problem: During startup, if I select Windows 10, the system boots into windows without any problem. But when I select Ubuntu, the system seems to go into a reboot (screen goes black), gives a POST like beep and then shows me the default GRUB screen (which I thought I had replaced with metro bootloader). This screen again asks me to choose between Ubuntu options and windows 10. Now I have to select Ubuntu once more and the system launches Ubuntu.
Question: How can I make the system boot directly (preventing additional GRUB screen) into Ubuntu once I select Ubuntu on windows bootloader? Is there a way to prevent the apparent reboot? And most important, what is causing this behavior?