Videos of edited Youtube playlist don't show up

Hi all,

my friend and I created a Youtube playlist with songs we like to listen to while gaming. We impoorted that playlist to Watch2Gether to listen to the same songs simultaneously. That worked pretty well and we enjoyed the shuffle playback.
Now we encountered a problem, though. We added more videos to the playlist. I didn’t expect the playlist in Watch2Gether to be updated accordingly, but even when trying to reimport the updated playlist, the newly added videos don’t show up in the playlist for the room. We tried it multiple times and even in new rooms. The playlist itself hasn’t even reached 200 videos yet.
Is this a known issue? Is this a problem with the playlist being cached and trying to import the updated playlist just grabs the former playlist out of the cache? If that’s the case, how do we circumvent this problem?

Thanks in advance.