Need to repeat first key during completion with FakeVim

When I'm using FakeVim and want to complete anything (either via automatic completion after '.'/'->' or manual via Ctrl-Space) then the first character typed is eaten and I have to repeat it. After first key repeated it works correctly - no need to repeat keys (until next completion, when situation repeats).
This is especially annoying with automatic completion.

It is my impression that this behaviour was not from the beginning - but it changed recently to show this annoying behaviour, but I cannot tell what caused this change.

When I turn off FakeVim then completion works correctly so only FakeVim is affected.

How can I debug this?

Regards
Andrzej