Error Code 0x8098011E Windows Backup Failed to get an exclusive lock on the EFI system Partition (ESP{)

First, restart your computer and try running the backup again before opening other applications. If the issue persists, I recommend performing a clean boot to determine whether a background application or service is interfering. Press Windows + R, type msconfig, and select OK. Under Services, select Hide all Microsoft services before clicking Disable all. Then open Task Manager > Startup apps and disable nonessential startup applications. Restart your computer and attempt the backup again. If it succeeds, a background application or service is likely responsible. Microsoft provides detailed instructions, including how to restore normal startup, here: How to perform a clean boot in Windows.

If the backup still fails after a clean boot, could you confirm whether you are using Microsoft Defender alone or another antivirus or security application? Finally, could you share a screenshot of the complete error message, including any additional error codes?