My A4 is the muts nuts with my HALO, faster than I can shoot! The same HALO on my IR3 was a blender. When my A4 arrived, I pulled it out of the box, put my Angel AIR and HALO on it, went outside and shot the whole damn hopper practically before I knew it was live. And that was before I did any trigger work! Mine's a Force 4 though, so it got inspected and tested by a master tech before it got to me, so perhaps it was already set up before I got it.
If you want to keep your HALO (I bought an Egg for my IR3, and hated it so much I decided to sell the marker and buy a 4 so I could use my HALO), you can try greasing the drive belt, that's supposed to help with it's hatred for some angels. Alot of people want to blame the angels, but since they're all machined at the same factory, to the same specs, and HALO's work on some, but not others, I'm more inclined to believe it's got something to do with the HALO software, or poor quality control on their drive parts, my personal opinion. I'm a firm believer in RTFM, but I understand wanting to go out and shoot your new toy right when you get it too (who wants to read the manual for 2 hours when the coolest marker they've ever seen just made it's way to their door?), that's why the best thing to do is just read up on the marker before you buy it, so you know what you're going to encounter.