There are no issues that are specific to customers updating from a previous release.
For security purposes, Pega-provided operators are disabled when you upgrade to Pega Smart Dispute for Acquirers 8.7. To continue to use any of these operators in your implementation, log in as an administrator and enable them. For details, see the Smart Dispute for Acquirers 8.7 Install Guide or Smart Dispute for Acquirers 8.7 Upgrade Guide.
Customized operators in your implementation are not affected. You can use them immediately after the upgrade.