Ouch. My eyes.
Remove the space in your can_target line of your headadmin group.
That's only a starting point. Likely won't fix.
I don't have time (or patience right now) to dig deeper, but, I've simplified your listing of your tree for you and others to look at below.
Some biggies I notice after list is simplified.
-Space in can_target of headadmin not co-owner.
-Superadmin can_target not themselves?
owner:
15 = ulx banip
16 = ulx cexec
38 = ulx rcon
inherit_from = co-owner
co-owner:
can_target = !%owner
inherit_from = headadmin
headadmin:
6 = ulx unban
can_target = !% co-owner
inherit_from = superadmin
superadmin:
7 = ulx ban
8 = ulx banid
can_target = !%superadmin
inherit_from = admin
admin:
allow:
3 = ulx ban
5 = ulx banid
can_target = !%superadmin
inherit_from = donatoradmin
donatoradmin:
can_target = !%admin
ulx ban = * 1440
inherit_from = vipmoderator
vipmoderator:
allow:
1 = ulx ban
2 = ulx banid
can_target = !%donatoradmin
inherit_from = moderator
moderator:
allow:
1 = ulx ban
2 = ulx banid
can_target = !%vipmoderator
inherit_from = donatormoderator
donatormoderator:
allow:
1 = ulx banid
ulx ban = * 2880
can_target = !%moderator
inherit_from = donator
donator:
can_target = !%donatormoderator
inherit_from = user
user:
can_target = !%donator