Just carried out some some experiments via new battle and it seems that the addCraft command fails when it's executed in any followup stage of a multi-stage mission. It works fine when the new battle calls it directly, but that only means it would also work in campaign if the mission was a single stage and you already started within the rift.
Tweaking one of the scripts, in this case the mushroom rift script, I 'borrowed' part of the entry block for the tower interior map and placed it IF the addCraft failed to execute thus creating an alternate spot for the player units to spawn. As you can see, it works 'flawlessly' if you don't consider the mismatch in terrain, but this is for testing purposes and an actual proper entry point map block could be made instead.
The modified code is as follows:
- type: MUSHROOMSCRIPT
commands:
- type: addBlock
size: 2
executions: 1
- type: addCraft
label: 1
craftName: STR_BRIFT00
- type: addBlock
conditionals: [-1]
rects:
- [1,2,1,1] #Place entry
size: [1, 1, 6]
verticalLevels:
- type: ground
terrain: MAGE_TOWER_INT
blocks: 0
size: [1, 1, 2]
- type: fillArea
Note how the addCraft now has a 'label: 1' and a whole new addBlock borrowed from the tower script, at least the important part, with a conditional added. While it doesn't direcly fix the issue with the addCraft it does give you a temporary workaround / failsafe to use.