I don't recall having that problem. I do remember wild Alpha Yutyrannus continually attacking even when KO'd though. Maybe that's related?

I've also noticed that aside from regular Ice Wyverns, none of the wyverns (alpha or normal) will use their bite attack when tamed unless you're riding them and manually use it.

Yeah ive had both of those happen too.

Unless its conflicting with one of the other mods installed, might just have to take them off one at a time see if any cure it.

Looks like it was Better Dinos mod not playing nice with EC, removed it and now the yuty is working fine!