Google confirms a "technical issue" on Google Maps "that caused the deletion of Timeline data for some people", but says those with backups can restore the data (Hadlee Simons/Android Authority)

Hadlee Simons / Android Authority:
Google confirms a “technical issue” on Google Maps “that caused the deletion of Timeline data for some people”, but says those with backups can restore the data  —  Update: Google has confirmed the issue, and it indeed advises affected users to restore their data via a previous backup.