If you build any Gregtech Multiblock, I tested it with the Multismelter or the Electric Blast Furnace, and use a MaxV Energy Input Hatch (everything other than MaxV works fine, the Voltage on the other Input and Output Blocks doesn't matter, they can be MaxV) you cannot open the controller, only the Inputs and Outputs. Trying to run the machine now by inputting any valid recipe leads to a crash - Even if you didn't power it yet.
crash-2020-04-08_15.31.04-server.txt

Known issue, yeah. It's a GTCE (well, SoG in this case) problem; on the modpack's side it's only possible to, for example, make it uncraftable.

This is a known issue, but unfortunately it's pretty much out of our hands.
The best we could do for now was to disable MAX Energy Input Hatches for 1.2.2.

That would at least solve it for now. If what i saw is correct (and still valid in the upcoming version(s)), it isn't used in any crafting recipes, no recipe goes over UV's 524288V limit, and thus it only has a use in multiblock overclocking, which leads to this crash.

Issue was fixed by Commit 202fbcce.