Default [Q] Can't flash PAC-Man with twrp


I installed twrp and used it to root my 2X without any issue. But for the last 24 hours, I am trying to flash PAC-Man and I don't understand what is wrong with what I am doing. I want to install + I downloaded the PAC-Man zip from basketbuild. I even downloaded it twice and compared the 2 zips just to be sure. In order to install, I uncheck zip zignature verification (else twrp refuses to do anything). I wipe my caches as recommended. When I press Install, I can see messages among which I can clearly see twrp open the 2 zips seemingly without any issues. At the end, twrp tells me the operation succeeded. But when I reboot, I find myself in v20s (which is my previous ROM).

Does someone have an idea of what is going on?

New tests. I did the same with cyanogenmod, the installation succeeded. Previously I did not know if it was my phone, twrp or the PAC-Man zip file. So now I guess it is the PAC-Man zip.