RE: "Crash detected" message during print
I'm seeing exactly the same issue. I3 Mk3S in an unheated enclosure. PLA prints just fine. ABS, get Y-Axis crashes and misalignment artefacts after the auto-home. If I turn of crash detection, the prints complete just fine with no defects. Belt tensions are within expected ranges and all bearings and rods are lubricated with the recommended grease.
RE: use another Einsy board case
I printed another einsy case (see below). There is much more space for cables, than in the original design. So, the stepper drivers will have more air to breathe. As cover I used the one with the additional spare for a fan. I used a noctua fan Noctua NF-A4x10 5V and pinned it directly on the empty 5V port of the Einst board. No problem with crash detection ever since. Another good thing is, that the board doesn't open in printer direction, as it opens now to the left side.
MK3s, Ender 5