I have spent a week re-reading everything on SWM8 installations, and I'm stuck. Sorry for yet another question on SWM installation, but I just can't figure this out. I know I'm overlooking something, and hope someone can spot my error. Last summer I installed a SWM-8 from my Slimline 5 dish, and round 72.5 dish since we still got locals from that satellite at the time. I kept my WB68 multiswitch and installed it in parallel for future use. My equipment at the time were three H10's, an HR20, two H20's and two H23's. I also use off-air. Installation was a breeze thanks to all the great info on dbstalk, and things worked flawlessly. I installed my SWM-8 inside my home near my cable distribution center. The four runs from the dish to the SWM-8 are about 20-25 feet. I installed the PI about 20 feet from the SWM-8. I used only one SWM port and terminated the other, running it to a SWS-8 splitter. I put my three H10's on the legacy ports and diplexed in off-air. I put the HR20, the two H20's and two H23's on the SWS-8 splitter and terminated the unused ports there. I like to use off-air on all my HDTV's from time to time, so I diplexed out at the TV's. No problems. My locals are switching from 72.5 and so I was notified I needed an equpiment upgrade, which in my case was just new boxes to replace the H10's. When the installer arrived last week, he looked at my setup with amazement. He knew somewhat about the SWM-8 but had never seen one. He said he was really only authorized to set up my new H23's through the WB68, which I expected. So we did this without any problems running them through the WB68. However, I do want to keep off-air, so after he left I then re-configured my setup. Obviously I previously had six tuners to my SWM-8, and now I have nine. Therefore I decided to run my two old H20's through the WB68 multiswitch using the BBC's, leaving my SWM-8 with seven tuners to feed. So, to recap, I have the SWM-8 and WB68 installed parallel from my Slimline 5 dish about 20 feet inside the house. PI is installed about 20 feet from my SWM-8. One SWM port on the SWM-8 feeds a SWS-8 splitter, the other is terminated. Antenna connected to the off-air port. Flex port is detached since I don't need the 72.5 sat anymore. No legacy ports used anymore. Two H20's attached to the WB68 with the BBC's installed before off-air is diplexed in. Both were set up without problems and work fine. Five H23's and one HR20 connected to the SWS-8 splitter, terminated the two unused ports on the 8-way splitter. Diplexer used at each HDTV where the H23's are, with off-air to the TV, and sat to the H23. Here's the problem. IF I use off air, I have trouble getting sat signals to any random box. Usually about 3 / 5 boxes work, the other two won't. This changes from box to box randomly, for no apparent reason. If I disconnect antenna from the off-air port of the SWM-8, OR take out the diplexer at each location, then all work fine. Why is diplexing screwing things up? I can't figure this out. I'm using D*-approved, high frequency splitters and diplexers everywhere. I'm using high-quality compression fittings and RG6 everywhere. I'm stumped, and can't figure out what I'm overlooking. Any ideas? Any help would be greatly appreciated. Thx.