Hi, thanks for reporting this. Can you give me a bit more information about your setup. I’m guessing that the bone name in this case is over 100 characters? And is this a control rig that you’ve authored yourself, or are you baking to an FK Control Rig?
I managed to get a repro on a very similar issue, although not quite the same ensure that you mentioned. The root of the problem appears to be an assumption in UFKControlRig::GetControlName that the bone name can simply have _CONTROL or _CURVE_CONTROL appended. But with long bone names, that can break the requirements of URigHierarchy::SanitizeName which will truncate the names. So we need to be consistent in how we are generating the control names and what we’re doing in GetSafeNewName. A full fix for this needs a bit of thinking about, so I’ve created a JIRA that you can track here.
I tested the workaround that you provided, but in the case of the repro that I found, I still hit a check failure in UFKControlRig::GetControlName. So it may be that you’re hitting a slightly different issue (which is why I was curious if you’re baking to FK Control Rig), or possibly you’re not seeing that if you’re running a build where checks aren’t enabled.