Couldn't find this problem answered anywhere.
Basically Lightroom has decided to take all the space it can on my Macintosh HD until it runs out of space. The problem stops if I shutdown Lightroom. The HD recovers the space taken after rebooting the Mac. I have purged the cache and optimise the catalog but the problem persists.
Is the space on the Mac Hd is filling up or the rem is getting eaten up.
Can you send us the screenshot for the activity monitor.
the Mac HD was filling up. Now it's fixed. I logged in into the Creative Cloud application and the problem has stopped now.