Solaris ZFS and reservations question

I'm having trouble increasing my reservations on some ZFS filesystems, although there seems to be enough space in the zpool, and no constraints on the parent device.

Note that I'm using refreservation instead of reservation, so I'm not constrained by the reservation on the parent device (or so I read it).

Output follows:

# Looks like plenty of space free in zpool "epool":
[root@host epool]# zpool list epool
NAME   SIZE  ALLOC   FREE  CAP  HEALTH  ALTROOT
epool  264G   176G  87.6G  66%  ONLINE  -

#  First, note that no reservations are set.  (I'm using refreservation so I don't have to calculate cumulative usage).   
[root@host epool]# zfs get reservation  |grep nds
epool/zones/nds21psfap001                reservation  none    local
epool/zones/nds21psfap001/app            reservation  none    local


# Here are my refreservation settings:
[root@host epool]# zfs get refreservation  |grep nds
epool/zones/nds21psfap001                refreservation  30G        local
epool/zones/nds21psfap001/app            refreservation  24G        local


# Here's where I try to increase my refreservations on my app filesystems - I can't increase them, even by one G!
[root@host epool]# zfs set refreservation=26G epool/zones/nds21psfap001/app
cannot set property for 'epool/zones/nds21psfap001/app': size is greater than available space

# Let's verify that there are not reservations on the parent devices that may be interfering:
[root@host  epool]# zfs get reservation,refreservation  epool/zones
NAME         PROPERTY        VALUE      SOURCE
epool/zones  reservation     none       default
epool/zones  refreservation  none       default

[root@host epool]# zfs get reservation,refreservation  epool
NAME   PROPERTY        VALUE      SOURCE
epool  reservation     none       default
epool  refreservation  none       default


Any ideas what may be happening here?

Can you post output of :

zfs get -r reservation,refreservation,quota,refquota epool
zfs list -t snapshot -r epool

Perhaps output of these commands above will clear things up and/or provide more precise information what is actually reserved on in epool.

Regards
Peasant.