I can't explain your phenomenon here. I can, however, invite you to my server where I can show off my GregTech factory, which happily runs three industrial grinders, an industrial blast furnace and an industrial electrolyzer (that's five 128 EU/t machines), plus assorted sub-LV machines behind LV transformers, off of two MV transformers.
You can however remove two of the connections to your transformer. The number of cables connected is entirely irrelevant, as any cable can transfer an unlimited amount of packets per tick. A single connection can easily handle an input of four packets per tick. If you connect multiple cables, you're potentially forcing the transformer to further split up its packets into for example two 43 EU packets and one 42 EU packet. Which should again not affect your industrial grinders.
I say should not, because it might, depending on what you do with the grinders. If they are out of juice and already have work waiting, then giving them too small packets may or may not cause them to fail to recover because it receives the first packet, consumes it, notices it is too small to satisfy its per-tick energy requirement and instantly stalls again. This is speculation on my part, because I'm not sure how the grinder works internally. However, there are other IC2 machines that show similar behavior. Try for example powering an empty luminator with a solar panel.
I'll also say that on my server, running GregTech 3.05g, I've encountered a bug where a GregTech machine that runs into Insufficient Energy Line even once will never recover again, regardless of how much energy I feed it. I have to wrench and replace the machine.