Your comments

1. Thank you very much, I believe keeping them in the range of 0 -> 360 could solve some issues.

Not sure what you mean by why Unity would record the keyframes that way. Isn't it skele that re calculates the IK targets/rotations/positions when using CDDSolvers every time you drag the keyframs back and forth causing the prefab model to get odd high euler values before you even start recording key frames? I mean this is something that occurs way before even trying to record keyframes. It's as if Skele thinks we are manually moving the targets once more when in fact we are just previewing the animation, and then messes up the calculations. Keeping them in range 0 - 360, could possibly just be a quick fix that ignores the underlying cause of it. But worth a shot to see if it actually fixes the bug.

2. Yeah I figured it was normal and just the way unity interprets the interpolation when insufficient information in keys. Though my issues haven't been in FK, only when using IK, but thought it might have been worth mentioning.

Best regards!

Just wanted to add, this is with latest version of Skele (1.9.4), and version 5.3.3f1 Unity.

I also saw other users having similar interpolation issues

Here, using just regular FK:

Here, also seems to be using FK:

Now the bug I presented is slightly different, yet the interpolation errors are a common factor, I don't know if they are any related. The way their limbs interpolate using FK seems to be completely Unity internal reliant. Still odd behaviours.