If I tap and hold a tab in Opera (version 39.0.2256.48 on Windows 10 Anniversary Update) to bring up the context menu, often the tab will detach from the tab bar. If I quickly notice this has happened I can try to drag it back to the tab bar, but it doesn't let me drop it back onto the bar nor does it show the up-arrow symbol to indicate where the tab would be dropped. Of course, if I don't notice it in time, the tab opens in a new window and I can then try dragging it back to the tab bar. This can be a pain, though, as I usually run Opera maximized.

Perhaps if Opera took a little longer checking for a long-press this wouldn't happen so often.

If I open a new page in Opera (currently on version 39.0.2256.48) on my Microsoft Surface Pro 3 (Windows 10 Anniversary Update) using any method (bookmark, link, address bar), after the page has loaded it often won't allow me to scroll the page, whether using the scroll bar, the track pad, or swiping the screen. I've found by experimentation that if I use the pen to tap the Reload icon or the Close Window icon, the page won't reload or close, but it seems to free up the scrolling.

This seems to happen with about 1 in 4 pages that I open but I haven't yet discovered why it does or does not happen with various pages.