Moving files causes the BEACHBALL.

Hi there!

If you think your Mac might have an issue, you can use this procedure to help gather information on your Mac which will help us troubleshoot your Mac’s problem.

To start, let us know what model your Mac is and what version of macOS you’re using. The simplest way to find out is About This Mac, available by choosing About This Mac from the Apple menu  in the upper-left corner of your screen. 

Next, share a screenshot of your Mac’s storage information. In the Finder, choose Go > Utilities, then double-click the Disk Utility icon. (Disk Utility is located in the /Applications/Utilities folder.) Alternatively, click Launchpad in the Dock, type Disk Utility in the search field, then click the Disk Utility icon. Once Disk Utility is open, take a screenshot of the information it automatically opens to, which will be your startup disk. Next, select View > Show All Devices in Disk Utility and select the non-indented disk entry—it’s at the top of the hierarchy. Then, take a screenshot of the newly selected entry. Upload all screenshots here. 

Next, use Apple Diagnostics to test your Mac to help determine which hardware component might be at fault. When testing is complete, Apple Diagnostics shows the results, including one or more reference codes.

Learn about Apple Diagnostics reference codes

Let us know which reference codes you receive.

Finally, let us know what antivirus, VPN, or cleaning software you have installed. 

Jack

First, by providing more information such as which iMac you are using, version of Mac OS installed, what troubleshooting you have already attempted, where you are moving files from and their destination. We are good however we are not mind-readers so we rely on your description so we have a good idea where to start.

I don't mean to sound terse but we are all end-users just like you and we need you to help us help you.

How much free space do you have on your boot drive and any external drives?