Try turning on context menu debug information, as described under "Finding the Culprit" here, to see which context menus items Opus is trying to display.
It looks like a bunch are missing so it's possible one of them is crashing when Opus queries it and that could be causing Opus to give up building the menu and display what it has so far. The debug output may indicate which extension is causing the conflict if that's the case.
Also, have a look under Preferences - Miscellaneous - Advanced: ignore_context_menus in case anything is listed there. If a menu crashes repeatedly, Opus may add it to the ignore list automatically. (The list is normally blank.)
PS: There's a FAQ on why post editing is disabled.