Wrong disk space usage in system information / backup problems

Hi all

yesterday i wanted to do Time Machine Backup which did not complete because of too little free disk space on my backup volume. I have a 1TB SSD in my Mac and free disk space on the backup volume is about 2,2 TB. Time Machine said, it would need about 2,4 TB. What the hell ....

So i did a small research and found that my Mac beliefs that an other user uses 2,5 TB of disk space. ???

Please the attached screenshot.

I have one other user with a profile of about 300 GB. Interestingly system information from this user shows correct disk usage.

In terminal there seems everything alright. df and du commands return correct results for disk usage.

So where does MacOS respectively Time Machine get these 2 and a half terabytes? I don´t know how to get Time Machine working or the disk space usage to a correct value.

Any ideas? Any help would be highly appreciated

Best regards
OK GO

 

really no ideas?