Rebuilding the EFI partition may leave Windows unable to boot - are you comfortable enough with your other OS to be able to restore the bootloader?
Instructions copied from here:
https://www.dell.com/support/articl...windows-7-8-81-and-10-on-your-dell-pc?lang=en
Rebuild EFI Boot Partition
Click the Start button, then choose the power icon.
Hold SHIFT and click Restart.
Choose Troubleshoot.
Select Command Prompt from the Advanced Options tab in the Troubleshoot screen :
Type and run the command :
diskpart
Type and run the command :
sel disk 0
Type and run the command :
list vol
Verify that the EFI partition (EPS) is using the FAT32 file system and assign a drive letter to it (Assign a letter that isn't already in use.):
Type and run the command :
sel vol <number of volume>
Type and run the command :
assign letter=<drive letter>:
Type and run the command :
exit
In order to repair the boot record :
Type and run the command :
cd /d <drive letter>:\EFI\Microsoft\Boot\
Type and run the command :
bootrec /FixBoot
Rebuild the BCD store
First run the command below to backup the old BCD :
ren BCD BCD.old
Now recreate it using this command :
bcdboot c:\Windows /l en-us /s <boot letter>: All
Note that the drive letter (C) may be different in your boot environment. Make sure you know which drive letters correspond to your boot, windows, etc. volumes.
