In file selector, right click a file, and choose to open it in a new tab (or just press middle mouse button on file name). => File downloads instead of opening in a new tab. This was reported against demo/tdf, but occurs in other LO Online versions as well. LOOLWSD master.. (git hash: 09fe0b6) LOKit LibreOffice 5.4.0.0.alpha0 (git hash: e4b6c3b)
I think you are talking about when online is used with a WOPI host ? If yes, then probably its more of a integration bug than online bug and there are already such bugs files on github against the plugin.
Right, let me close this one as MOVED.