can not syncing after restart

[Thinkre]

I did any changes in both two devices. After reopening app on my android device, it shows me error:"folder marker missing (this indicates potential data loss, search docs/forum to get information about how to proceed)". When I create a folder named as '.stfloder' in root of my sync directory, it works again. It seems .stfolder missing(I did nothing about it). Is there a way omit this error?