TiTS is buggy because the creators were forced to play fast and loose with converting it from a Flash game into a Java game when Flash was pulled from browsers. They could have of course gone the slow route to prevent bugs and the like, but that would have created the problem of drawing money from supporters every month and not having anything to "show" for it until they got the Java version up to snuff.
So they went quick and dirty, keeping everyone in the loop and up to date with everything they were doing under the hood, and battling the tides of bugs and glitches as much as they can as they go. It was a huge setback, but everyone was pretty understanding. We've all been hit by the loss of Flash in browsers.
Inversely, CoC2 was already a Java game to begin with, so wasn't really affected by the loss of Flash like TiTS was. Bugs are always gonna be a thing, but the lack of fast conversion kept it manageable.