EDIT: This has been fixed in version 1.41!
I know why there’s a bug related to the HUD not being centered in the version v1.21! I I found that bug reoccurring in GZDoom 4.6 and 4.5.
The line 55 of the file “SBARINFO” in the Mayhem Mansion PK3 is the one causing that problem. Replace that…
drawimage "STBAR", -134, 164;
… with this.
drawimage "STBAR", 0, 164;
I used Slade to find and edit the file.