I’m getting dropouts in Lx5 on my Pal master system. They’ll usually start after 10-15 mins of play and increase in frequency to roughly every 5 mins. Strange thing is that it doesn’t do it in any other mode than x5. I’m using pretty much standard settings with only V.active and V back porch tweaks to get a picture.
Sounds like maybe your HDMI cable doesn’t have enough bandwidth for the x5 mode, causing the signal to drop out. That would explain why the lower modes work. Have you tried another cable or maybe even another display? Also make sure your cable isn’t over 7 meters long unless it’s an active cable.
Tried a different HDMI cable (the one that came with my Xbox One X) and no different. It always catches me by surprise so I’ve never managed to see if it’s the OSSC losing sync. I suspect it’s the oddball refresh of a PAL MS causing the problem so I’m probably stuck with Lx3 but it’s not really a big deal