When using arrow keys to scroll, some keystrokes are ignored

Describe the bug
When scrolling with up and down arrow keys, some keystrokes are ignored or not processed.

To Reproduce
Steps to reproduce the behavior:

1. Go to any page which is scrollable and does not have any scripted scrolling behavior
2. Rapidly press the down arrow key three times
3. Note how many times the page has scrolled (two for me)
4. Disable Vimium completely
5. Return to the same page
6. Rapidly press the down arrow key three times
7. Note that the page has scrolled three times, and is further down than after step 3

Expected
In steps 2-3 and 6-7, page has scrolled the same number of times, and the same distance.

Actual
Page only scrolls twice in steps 2-3
Page scrolls three times in steps 6-7

Notes
This bug does not reproduce reliably for me, only about half the time.
The arrow keys must be pressed rapidly in succession.
Page Up and Page Down keys are also affected.

Vimium: 1.66
Browser: Chromium Version 88.0.4324.150 (Official Build) for Linux Mint (64-bit)

No source file or test is named. Start by reproducing the issue in Chromium with Vimium enabled and disabled, using rapid arrow, Page Up, and Page Down presses; then trace the keyboard handling involved. Done means rapid key presses scroll the same number of times and by the same distance as with Vimium disabled.