Lightroom performance laggy when clicking on filmstrip at bottom

I am using Lightroom version 7.4.1 (non Classic version)  on my new Macbook Pro (M3 chip), with 16GB memory and 1TB disk.  MacOS is Sonoma 14.6.  When I click on each of the photos in the filmstrip at the bottom of Lightroom,  it takes about 5 seconds before the bigger image appears on the panel above.  I expect it to be around 1 second.  So it is very laggy.  I noticed from the Activity Monitor  that CPU usage spikes to around 140% whenever I click on a photo in the filmstrip.  It is that way even though there are only 3 photos in the filmstrip. I have shutdown other applications. I have cleared cache and ensure the GPU use is in "Auto" under Preference. 

What could be wrong and how could it be fixed? Thanks.