Windows 10 IME kanji dropdown list and spacebar behavior

[tmahrt]

On my IME when I type katakana a menu pops up with kanji substitutions. I thought the space bar would select the one off the top and then hitting space again would give me the second one on the list. Instead, hitting it once gives me the first one off the top and hitting it a second time pulls up a completely different list!

So さんぽん’s menu for me has 1) 散歩ん and then 2) 三本杉. But if I click space bar twice I get さんポン with a new completely different list. [EDIT: if I click the space bar a third time, it navigates through this list as I would expect it–it does not bring up a third list, etc.]

In order to select option 2 from the first list, I have to use the mouse or arrows to navigate to the item.

Any ideas whats going on and what I’m doing wrong?

[tmahrt]

More observations:

If I hit tab, I can ‘enter’ the first list. After entering, hitting space here does navigate me through the list, rather than taking me to the second.

If I don’t hit tab, hitting space twice brings up a second kanji substitution list that is different from the first. Hitting space more than twice, navigates through this second list. The first list usually contains the word I want and the second list sometimes does but often doesn’t.

There don’t appear to be any options in Windows 10 to configure the IME and no internal information as to what this behavior is.