Verification only half-completes - left waiting for confirmation

Between the linux Desktop client and chromium Web client, the non-legacy verification does not complete for the Desktop client. After the emoji verification, we are left with a spinning dialogue:


The desktop client is also left waiting for confirmation.

After clicking back into the compose message window, the dialogue disappears and apparently cancels the remaining verification, leaving the Web client to see the Desktop client as verified (green shield), but the Desktop client does NOT see the Web client as verified (red shield).

The only way around this was to use the Legacy method to verify the Web client session.

Versions
riot-web version: 1.5.15
olm version: 3.1.3

Reproduce non-legacy emoji verification between the Linux Desktop client and Chromium Web client using the reported versions, then trace the verification flow from the spinning dialogue and confirmation state. Done means both clients complete verification and show each other as verified without cancelling when returning to the compose window.

Written by the indexing model from the issue text.