Sending data to RHDG configured with Protostream serialization (which is our recommended configuration), which contains circular object references will cause it to go into an infinite loop until it maxes out the thread stack.
This issue has been addressed in the following products: Red Hat Data Grid 8.4.4 Via RHSA-2023:5396 https://access.redhat.com/errata/RHSA-2023:5396