So I have tried the suggested configuration and am still having trouble.
Running show ltm persistence persist-records all-properties I receive the following output: (Note I have truncated the output to preserve space)
-----output truncated-------
universal - 10.x.x.170:1813 - 10.x.x.172:any
----------------------------------------------------
TMM 2
Mode universal
Value 141.x.x.115
Age (sec.) 18
Virtual Name /Common/ISE_Radius_account
Virtual Addr 10.x.x.170:1813
Node Addr 10.x.x.172:any
Pool Name /Common/ISE_model_server
Client Addr ::
Owner entry
universal - 10.x.x.170:1813 - 10.x.x.172:any
----------------------------------------------------
TMM 1
Mode universal
Value 141.x.x.115
Age (sec.) 18
Virtual Name /Common/ISE_Radius_account
Virtual Addr 10.x.x.170:1813
Node Addr 10.x.x.172:any
Pool Name /Common/ISE_model_server
Client Addr ::
Local entry
===================================================
-----output truncated-------
source-address - 10.x.x.170:1812 - 10.x.x.171:any
---------------------------------------------------------
TMM 1
Mode source-address
Value 141.x.x.166
Age (sec.) 145
Virtual Name /Common/ISE_Radius_auth
Virtual Addr 10.x.x.170:1812
Node Addr 10.x.x.171:any
Pool Name /Common/ISE_model_server
Client Addr 141.x.x.166
Owner entry
The last record is the RADIUS client that all other records should be persisting to.