I am using Doom legacy 1.44 alpha4 with the original full doom.wad. I noticed if I am running up for example, nothing will happen when i hit left until i let go of the up key. There are a few other minor combinations in which keys like that will not register while another one is being held down. I think down and right works fine, for example. In the old days, I used to run and gun like this all the time, and this is very restrictive and I believe essential to beating the game on Ultra Violence. Thanks for reading my bug report.