Time Machine won't backup after upgrade to 10.14.4

I spend some time on the phone with support and we reset the SMC and the NVRAM and it's been working since then. Time Machine has backed up several times and I am not getting the error. Fingers x'd it stays that way.

Reset NVRAM or PRAM on your Mac 

How to reset the System Management Controller (SMC) on your Mac 

had same problem after upgrade to 10.14.4

was able to fix and get time machine back up again with help from Apple support - after doing a forced hard shutdown and restart.

hold the on/off button until the system shuts down (all unsaved work will be lost). then restart by pressing the on/off button.

note - it did not fix the issue when I forced kill all open applications, or a restart of mac os. it needed the hard shutdown/start in my case.

Go into macOS Recovery (turn on your iMac and immediately press and hold the Command (⌘) key and the letter R on your keyboard until the Apple logo or spinning globe appears on your screen, then let go of the keys). Wait for the macOS Utilities window to appear on your screen, then choose Disk Utility, then press Continue and run First Aid on the Startup Volume, which is most likely your Macintosh HD. After First Aid repairs it or says that it's successfully completed the check on your Macintosh HD (with a white checkmark and an OK on a green background), shut down your iMac. Boot up your iMac normally, plug in your External HD for Time Machine backups to your iMac, and now you should be able to immediately begin backups on Time Machine. Please note: The preparing backup sequence on Time Machine will initially take awhile (like maybe 45 minutes or more) before Time Machine begins backing up.

Be aware that you can get quite a number of backups done on multiple backup disks for several days, before you may have to do it again (the procedure isn't too time-consuming anyway), but at least it's a quick fix to that devilish red circle with the "little white i" inside of it on the Time Machine window.   

Try booting into Safe Mode, and see if you can get a backup from there to complete. Then reboot normally and try again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing.

I read this thread, tried everything, both before and after calling Apple support , when the third agent I talk to suggested looking at software update.

While the update was progressing I got another call from Apple Senior support suggesting that over writing the operating system while in recovery mode would also work ..

When the update to 10.14.5 finished the back up succeeded .

Since then I have attempted another back up but was unable to tell before I left the house if it was going to succeed... although given the intractability of the initial problem I’m optimistic that it probably will.

I reset SMC & have had 2 successful backups so far ! Here's hoping.

same for me

time machine works fine since 10.14.5

and warmd is no longer on top of the processes during hours after reboot as it was the case with 10.14.4 (in activity monitor)

in 10.14.4, after a reboot, I had to wait many hours the "extinction" of warmd before being able to do time machine without the error message.

For me (a never in use) FileVault kept on blocking TimeMachine only with 'automatic backups' unticked

So, if I temporally tick 'automatic backups', then I am able to run the backup successfully

warmd controls caches used during startup and login. It is a launch daemon started by launchd during boot and is not meant to be invoked directly.

Could be a corrupt cache file. Boot into Safe Mode, to clear out the system caches. Reboot normally and check Activity Monitor again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing.

Me too. Long day of failed support, tried everything, Apple Senior support retracing the same ground over and over - until we tried using Software Update to install 10.14.5 (just out).

Problem solved.

I did get a special callback, a senior guy who just solved this for someone told me to restore the system in Recovery mode.. but installing 10.14.5 did the trick before I had to resort to that.

I had the same problem with my MBP only the hard shutdown worked & have made 5 successful backups ( I backup once per day) after the one hard shutdown - here's hoping ......

update 10.14.5 looking good for me so far. will feedback again should the failure symptoms return.

safe boot or any of their two suggestions did not work for me unfortunately.

Hard restart, backup worked once - is a workaround for some of us (not everyone has this ongoing TM issue).

it’s recommended to contact Apple support and get this issue logged, for those of us having to live with this bug ?

I have had two sessions online chat with Apple, and two phone calls from Apple and so far they have gathered info from my macOS to pass on to their macOS team with no fix yet. but I use the workaround suggested above in the meantime.

we think it is a bug?

Hard restart, backup worked once - is a workaround for some of us until they come up with a fix since macOS 10.14.4.

same problem

I saw in activity monitor :

since 10.14.4 there is a processus that is at the first place : warmd

it is in activity during many hours

then it stops

when warmd is active, i cannot do time machine and there is the error message with filevault (like the others, file vault is not activated on my computer)

when warmd is becoming inactive I can do time machine

in the past, when I was with 10.14.3, I had not paid attention to warmd ! it was not prominent

any ideas ???