Issues with Special Ninja Squad (homebrew)

[Vectrex28]

Hello!

I'm the developer of Special Ninja Squad, a homebrew with a recently released demo for the PC Engine.

I've gotten a bug report that Beetle PCE Fast does not play the game properly and has garbled graphics.
This seems to be due to incorrect handling of VRAM readback - my decompression routine does use VRR extensively and it seems to match with a specific decompression case.

The ROM is available on this link
https://vectrex28.itch.io/ninja-squad

Recreation steps

1. Launch the ROM in Beetle PCE Fast
2. Do nothing until the game shows the screen below in the cutscene
3. The whole picture is garbled

*NB: There are other graphical glitches due to this prior to the scene in question - I showed this one in particular as it is most apparent

Beetle PCE Fast:

Correct behaviour:

Thanks in advance!