In the course of many swaps of single cables leaving everything else unchanged, we thought we had identified some cables that almost always worked and some that usually didn't. For the most part this testing was 2 jags connected to BDC-Comm, with "works" defined as both units showing up in the program's device menu. However, the cables weren't 100% consistent. Sometimes a "good" one failed to pass, and I'm not positive the "bad" ones always failed. But clearly some worked more often than others. When we tried to put together all four with the better cables, we got all four to show up once, after that never got the last one to appear. Reordering the chain moved the failure to whichever one was last, though we stopped testing before running through all combinations. A few days ago I was able to get all four to show up in BDC-Comm, then got errors trying to access them from a program.
These modular crimp connectors seem pretty foolproof to me. Other than simply getting them backwards, which I'm sure we didn't do, is there any way to mess them up? We have used this same bunch (we have ten or so) of jags many years without any such issues, and now they're suddenly all flaky. The only thing obviously different is the physical layout (usually we put them all in a close group) and the wires. Using generic part-swapping troubleshooting methods, we've been having a terrible time isolating the problem to any particular device or cable, and it just doesn't make sense to suppose simultaneous failure in many parts that have worked so well for so long. It seems like it just HAS to be the cables, but I'm baffled as to where and how; they seem so simple.
Inspecting the connectors inside the Jaguars is an idea we hadn't had, though we did do a little "wiggle" testing to no apparent effect. That will be first on the todo list when we hit it tomorrow.
Thanks to everyone for the ideas and suggestions. We're on the verge of pulling the whole blasted thing and dropping in some old-school PWM Victors, but this problem has to have a solution, and one hates to admit defeat before even taking the field
Edit: A general shortening of the wires sounds like a good thing to try too. We've been testing with a big pile of cables, most of which are 3' long or so. We could probably cut the total chain length in half by cutting to exact lengths. It would still be longer than we've used in the past, but much shorter than what we've been trying.