DraStic

First of all, i want to congratulate the devs of drastic for the amazing improvement of the emulator with the addition to play in high resolution mode. That's a really big milestone for emulation in general.
Anyways, i want to ask if it is possible to fix the bugs on the multi-threaded mode (objects displaying on the wrong screen), or is it a really technical issue that cannot be fixed at all?
The question why i'm asking this is because the new high resolution mode is very demanding.
I can play really graphically heavy games with little to no framedrops and at high resolution on my phone, but only if i have the multi-treaded option enabled, however, enabling this causes some games to be not as playable (dragon quest 4,5,6, Etrian odyssey), and disabling the option causes a really big impact on performance.

The way the multi-threaded mode works right now is the 3D is behind by a whole frame. If you don't do this there's very little speedup. But it causes the 3D and 2D to become out of sync, which causes the glitches you see. It's inherent to the approach.

Trying to make the 2D also behind a frame has a bunch of problems and overheads of its own, and could still cause some other problems. I don't think this is really the suitable alternative.

I have a design idea where the 3D is only behind by a small part of a frame. It could perform a little worse because it splits up 2D rendering into multiple chunks and because the first chunk doesn't allow for parallelism. But it shouldn't have the glitches the current mode has. It'd be a totally different approach so a major code redesign, not something that can be implemented trivially.

I see, so it uses a clever method to manage a 3D speedup , and that's why 2D based games are the most affected for it. Now it makes a lot of sense.
Well, i'm looking fordward to the implementation of your idea if it ever gets done, because it does sound like a complex feature to add taking in count you have to redesign the code of Drastic.

Many thanks for the answer! it did help me to understand the reason of the bugs.