If your Panel Memory is changing after the initial 'correct' four bars then this is what is causing your problem. All the sounds which your see in the Sequencer Mixer, are affected by the content of the Panel Memories. As your Panel Memories change, they will select whatever sounds have been stored in the particular Panel Memory, for other tracks. So, you need to change the sound assignments for the additional tracks you wish to use in the sequence.
You won't lose your currently set voices in Panel Memory, to achieve the result you desire.

There is more than one way to achive this - the method I use is as follows :

Select your first Panel Memory (eg PM1) and then in the sequencer Mixer, press the top left button at the side of the display to highlight the 'SOUND' section. Press the track number button at the bottom of the display, for the track you wish to assign a particular sound - the 'SOUND' highlight will move to the selected track. Use the 'Sound' buttons to select the desired sound and then press 'SET' and the Panel Memory button you chose at the the start of this procedure (eg PM1). This has the effect of storing the selected sound in the new track, along with your original Panel Memory settings.
Just repeat this process, for each Panel Memory used in your sequence or performance set-up. When you have made all the changes you can then play through your sequence or performance and the Panel Memory changes will select the correct sounds for your additional tracks.

If you intend adding more than 1 track to your original 'Easy Record' sequence, then just assign new sounds to all the required tracks, before Re-storing to Panel Memory.

You can achieve the same result by using the 'Part Setting' facility but having assigned a new voice to a particular part, you must then Re-store each change in the appropriate Panel Memory

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Willum