Why is macOS Sequoia 15.3.1 Time Machine reformatting APFS to APFS case sensitive and slowing down backups?

Same Problem after Sequoia 15.3.1. It backs up my Data but not the external drive. Never use to have the problem. I've adjusted the sleep mode etc. to avoid that as an issue- still doesn't do my external. They are both set up as APFS, non case sensitive, which I read that case sensitive is more of a problem. I did notice the even though my external drive is encrypted and password protected, 15.3.1 doesn't ask for the password- it automatically mounts. I found that strange, and erased my Time Machine and re did it again with password & encryption and before mounting it asks for password. So why does my external drive, originally set up and encrypted with Ventura and always requested the password now not need it??

I've been using Time Machine since the beginning and no issues until now. I've tried most of the suggested fixes from the community but they haven't solved the issue. Bottom line: currently with Time Machine It backs up only the Mac HD data etc. When I open Time Machine, I see my external drive image positioned below the Data Drive but nothing is populated in it. I'm thinking about going back to AWE Clone which always worked.

Suggestions that I haven't tried??

Razorback007 wrote:

I have used Time Machine for years to back up on a APFS formatted external drive, eve with Sequoia 15.3.0, no problem ! It usually takes about an hour.

I upgraded to Sequoia 15.3.1, now, Time Machine is indicating it will take 24 hours +,-.

I stopped the backup, and used disk utility to check, then erase the drive, and to reformat it again in APFS.

HOWEVER, I noticed the drive was reformatted by a glitch (?) in Time Machine to APFS CASE SENSITIVE format. I’ve tried this 3 times, Same result.

I have noticed other MAC users are having strange issues with TIME MACHINE in Sequoia 15.3.1 also…….

TIME MACHINE is APPLE’s bedrock, time tested, trusted backup program.

i also use Carbon Copy Cloner on another external drive using Sequoia 15.3.1 with NO ISSUES.

I’m looking forward to a (hopefully soon) future update to get this nasty worm out of my Apple’s IOS.

[Re-Titled by Moderator]

Is your Internal drive Case Sensitive...?

As far as I know Time Machine does use case sensitive format.

the Learn more about backup disks that you can use with Time Machine —Backup disks you can use with Time Machine - Apple Support

My last two TM drives both formatted to case sensitive by default. I see no issue doing that. Both Mac TM drives work fine.