Yes, I had a similar issue on my windows client (10.57.6) : I lost a text line I added a few hours ago to an existing note. This line was still there in the current history version which should be the same as my clients version! I tried to synchronize but it didn't appear in my clients...
Edit: after thinking it through, a little bit more context:
I created the note on my android phone, closed the note and put my phone to sleep.
I went home and tried to open that note in my windows client. The note was there but the pictures wouldn't load.
In order to get the images, I opened my note on my phone again. Immediately the pictures arrived in my open note on the windows client.
I added the single line of text in the windows client
I closed the note in android and windows
a few hours later I discovered that the text line was not there anymore as described above
Conclusion: this is a merge problem, a little bit unexpected considering that Yjs keeps update timestamps to identify the order of updates and to resolve conflicts. This mechanism seems to have failed in this case...