It seems the last channel gets lost when using PIP on the current beta.
For example you are on channel 17.1. Then you hit back on the remote to go back to the guide while PIP is active. Then you hit 23.11. Then Full size the screen. If you hit back to go back to the guide again. The last channel it highlights will be before 17.1, instead of 23.11 which is currently playing in PIP.