Microsoft RDP - Getting sent to wrong pool member while using Session Broker

I have an interesting issue with my MSRDP environment. We have two virtual servers listening on TCP and UDP 3389, with two pool members (Server 2016). The configuration is set up per the deployment guide. ][https://goo.gl/3mVMLd] which us using Session Broker, but no Gateway.

Occasionally, the customer is getting sent to the wrong server, which causes the UDP feature to disappear.

This is when it's working:

tmsh show ltm persistence persist-records

source-address  192.168.75.73   192.168.246.114:3389  192.168.72.141:3389    (slot/tmm: 1/0)
source-address  192.168.75.73  192.168.246.114:3389  192.168.72.141:3389  (slot/tmm: 2/0)

Here is when it fails:

tmsh show ltm persistence persist-records
msrdp           DOMAIN\notarealuserid  192.168.246.114:3389  **192.168.72.150:3389**   (slot/tmm: 1/0)
source-address  192.168.151.243  192.168.246.114:3389  **192.168.72.141:3389**  (slot/tmm: 2/0)

When it fails, the persistence record shows the customer going to different pool member. However, I don't understand why, when it's working, that the persistence records are only showing source address and not msrdp.

My question is two parts then.

1) Why is the persistence record only showing source-address? Is this only a persistence record for the UDP virtual server?

2) When the UDP feature fails, why is the user being sent to the wrong node SOMETIMES?

Thanks!