If a VTI interface is disabled in a configuration, it can be reenabled by the up-client or up-host events.
Most likely, primarily this bug exists because a small typo in the vyatta-vti-config.pl:

my $disabled = $vcIntf->existsOrig("vti $intfName disabled");

But interface settings contain the disable option, not disabled.

We need to fix this and recheck.