Intermittently keyboard doesn't work at boot picker

Issue: Keyboard doesn't work at boot menu but mouse is working.

Configuration:

1. Opencore 0.5.9 and Catalina
2. FileVault is active
3. MB: Q370
4. CPU 8700
5. Keyboard: Apple USB white keyboard connected directly to MB USB port

I'm always able to reproduce this issue from cold boot but this intermittently happens during reboot. Only way I'm able to get my keyboard to work is by doing multiple power cycles. Followed the instructions here to configure OpenCore with FileVault. Tried following combinations and issue reproducible both ways.

1. KeySupport: true and no OpenUsbKbDxe.efi
2. KeySupport: false and with OpenUsbKbDxe.efi

NOTE: This does not happen if i use clover boot loader.

Appreciate any help to fix this problem.