Integrity Error when upgrading to V12

Switched to branch version-11 and updated to latest version 11 .64 successfully.

After that tried to switch to branch version-12 encountered missing doctype error “Milestone Tracker” and someone mentioned in another thread just create back the entry under tabDocType and it worked.

Second problem, not sure what is the cause:
It occured during:
Executing frappe.patches.v12_0.move_timeline_links_to_dynamic_links in site1.local
pymysql.err.IntegrityError: (1062, “Duplicate entry ‘1000000001’ for key ‘PRIMARY’”)

Any idea how to get this fixed? Switching back to version-11 now.

After a branch switch, you normally need to run a bench update --patch to sync the DB schema’s

I found the error, it’s actually a row inside the tabCommunication Link table
not sure how it got there, but it worked after we deleted that entry.