Before/after toggle has a 1-2 second delay?

I've only used LrC for film photo scans (JPG) prior to this, where pressing "\" (backslash) key to toggle between before and after was nearly instantaneous. 

I imported a bunch of digital camera .dng's today and noticed that when working on .dng files, the "\" before-vs-after toggle takes 1-2 seconds to finish. My cursor would spin the rainbow beachball while LrC is at it. 

Is this normal? I don't know why it'd would spin for a couple of seconds to for .dng files.

Version: 11.4.1

Platform: macOS Monterey 12.5