@Litjan
The problem is the nose gear type of Ixeg 1.3, It was changed from 3 (double) to 2 (single) and the PushBack tug can´t handle single gear.
There are 2 fix workarounds:
Change the P _gear/0/_gear_type in ACF from 2 to 3
Or
Open the file info.cfg in folder \X-Plane 11\Resources\plugins\BetterPushback\objects\tugs\AST-1X.tug and change the line "gear_compat" to "ff"