iTunes: How to find backup corresponding to a particular version of iOS?
If you have an old 12.3.1 backup of your iPhone, you can restore your iphone from that backup.

Then you have to delete (or drag outside the folder) your 12.3.2 backup so that iTunes restore your device from the new "latest one".

from Apple support :

Find iOS backups on your Mac

Find a list of your backups:


Click Search icon in the menu bar.
Type or copy and paste this: ~/Library/Application Support/MobileSync/Backup/
Press Return.


OR

Locate a specific backup:


Open iTunes. Click iTunes in the menu bar, then choose Preferences.
Click Devices.
Control-click the backup that you want, then choose Show in Finder.