RoPieee v160 progress bar shows up and down

I have two RoPiees for each zone on my roon network. Both RoPiees has own 7" display.
When roon plays some musics for each zones at a same time, progress bar on 7" display shows up & down. It seems both zones progresses are shown in each in 500? msec.
Other infomation on 7" display are OK i.e. album arts, titles, artist names. Also sounds on each zones are OK.

I can still enjoy the music itself so no urgent requirement to fix but please look this in sometime.