Maybe think the mechanism is sticking?

It could be when you press the button underneath the hatch the slight upward pressure helps the mechanism fully disengage.

Pressing the keyfob to open, the mechanism must cycle open without any help and might be sticking enough to cause what you are experiencing.

Maybe you could spray the mechanism as up suggested, while cycling the soft close manually?

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04 X5 3.0i auto
03 X5 4.6is