Hey, @こき. Welcome to the Lightroom Community. Thank you for the report.
I can recreate this, and I'll share it with the team for review. For now, it just required a few extra clicks to get back to work: Click on any other image in the filmstrip, click on the Grid view icon or press G on the keyboard > click on any image in the grid, and the arrows continued to function.
Let me know if this helps.
Sameer K
(Type '@' and type my name to mention me when you reply)