rP19694 forgot to remove the territory decay disabling of the spikes too.
So on Danubius, the gaia fortification will have it's walls being converted to the player,
then the gaia units destroy its own walls, except the spikes.
There must be an uncapturable special filter once it's supported by the AI.
For the current release (a22), it might be best to not add workaround templates and not commit this fix.