Unable to achieve session persistence through Persistence profile and iRule

Hi,
We are trying to achieve sticky session based on header in the request.
This is the cofiguration we currently have in the setup:
A pool with loadbalancing algorithm as "Round Robbin" with 2 nodes.
Created an iRule with the following configuration where "sessionid" is the header based on which we need persistence.

when HTTP_REQUEST {
    if { [HTTP::header exists "sessionid"] } {
        persist uie [HTTP::header "sessionid"]
    }
}

Created a universal persistence profile based on the above iRule with a timeout of 1 hour.
Attached both iRule and persistence profile to VIP created over the required pool.

Expectation:
All the requests which are within persistence timeout with the same header value should be routed to same node in the pool.

Current Behaviour:
The requests which are well within timeout with same header value are routed to different nodes and the requests are failing.
Also, tried modifying iRule to config set in this KB, but that did not work as well: https://support.f5.com/csp/article/K7392
As the requests are within timeout and are still failing, I think the issue is not with timeout configuration and something with iRule. Can someone please help on how we modify the configuration in order to meet the requirement.