Identity Governance proprties like
portalExternalLink.homeUrl
portalExternalLink.certificationUrl
portalExternalLink.ticketQueueUrl
if changed after deployment will be reverted back to default values after node is undeployed or deployed.
Identity Governance 14.5.X
Fix for he issue will be released as part of next 14.5 SP, CHF after 14.5 SP1 CHF1 or v15 Fixpack 2.
Please reach out to the support team of you need hotfix before that.