Game UI fully locks up from presumed race condition when refining relics on in-mission relic select screen, requiring client restart

[-SMG-]

Steps to reproduce:

• Start an endless mission with at least one other squadmate
• Complete at least one rotation of the mission
• Wait until you get to the relic selection screen for the next rotation
• Instruct one teammate to not select a relic until you tell them to
• Select a relic to use for the next rotation
• Select any other other refine-able relic, and refine it
• While the loading element for the refinement is showing (presumably while the network request is still inflight), have the last teammate select their relic for the next rotation
  • I would suspect that the network traffic from your teammate selecting their relic would have to reach your game client before the response to the refinement request, but I don't know this for a fact

Expected behavior:

• The loading element from refining disappears from the screen
• All UI elements related to relic selection disappear as they would normally
• The game continues to accept user input, and the cursor is hidden

Actual behavior:

• The loading element from refining remains on screen until the game is killed
• Menus under the loading element progress normally (showing the squad's selected relics, then disappearing)
• The game does not accept any user input even after the relic selection and display elements disappear normally (e.g. in-game actions, esc key, chat key, etc.)
• The mouse cursor remains on screen indefinitely and can be moved, but does not do anything
• The game must be completely killed and reloaded to continue playing

I have personally repro'd this issue on Steel Path Void Cascade last night (patch 35.5.6). Don't have a recording of when it happened, however.