Syncthing tells me that many objects could not be synchronized.
Does anyone know what objects are and if I can just delete them?
The filename has characters that are invalid on windows, so it can’t be downloaded. What you want to do about it is up to you. You can ignore them or delete them, it’s up to you.
The folder /streams is probably created by QNAP and I sync my Windows machine with a QNAP NAS.
see also: https://forum.qnap.com/viewtopic.php?t=132545 (how to handle .streams folders)