Migrate data using JCMA cannot complete pre-checks due to "We couldn't check for invalid users"

Issue Summary

This is reproducible on Data Center: (no)

Steps to Reproduce

1. Create a migration plan in JCMA
2. Run pre-checks

Expected Results

Pre-checks is completed

Actual Results

Pre-check is failed and the following messages are shown.
・We couldn't check for invalid users
・We couldn't check for duplicated users

The below exception is thrown in the xxxxxxx.log file:

Caused by: com.atlassian.jira.migration.preflight.ums.exceptions.UmsPreflightCheckException: User Group Extraction or Data Upload Failed
	at com.atlassian.jira.migration.preflight.ums.UmsPreflightService.cleanUmsPreflightCheckFileId(UmsPreflightService.kt:117)
	at com.atlassian.jira.migration.preflight.ums.UmsPreflightService.cleanUmsPreflightChecksResults(UmsPreflightService.kt:111)
	at com.atlassian.jira.migration.preflight.ums.UmsPreflightService.executeUmsPreflightChecks(UmsPreflightService.kt:76)
	at com.atlassian.jira.migration.preflight.ums.UmsPreflightService.executeUmsPreflightChecks(UmsPreflightService.kt:33)
	at com.atlassian.jira.migration.preflight.UmsInvalidEmailService.validate(UmsInvalidEmailService.kt:37)

Workaround

1. Go to <your-jira.com>/secure/migration-app-action.jspa#/email-validation/fix-invalid-emails
2. Select Do nothing with invalid users option
3. Go to <your-jira.com>/secure/migration-app-action.jspa#/email-validation/fix-duplicated-emails
4. Select Do nothing with duplicated users option
5. Click Review and apply
6. Click Assess again and resolve issues with invalid and duplicated emails if any are present, ie. select Change settings and choose your preferred option for fixing invalid/duplicated emails
7. Click Apply to all migrations
8. Go back to your migration or start a new one, pre-migration checks for invalid and duplicated emails should be passing

If above workaround didn't solve the issue, and the error happens during scoped migration, on step 6 do not fix invalid/duplicated users - after assessing again just select Apply to all migrations. User assessment as a whole will be red, but your scoped migration will pass. Make sure not to fix the users that are not a part of migration.