If you call down a rescue drone for an animal as Operator, you are able to use transference to then go into a necramech.
When you exit the mech, you lose the ability to switch back to operator or to enter the mech again. Transference becomes usable again in the openworld's relay, but remains unusable in the Drift itself until you return to the orbiter.
Transference (or at least into anything except a warframe) should not be usable while capturing animals.
I haven't tested this outside solo or in the Vallis/Plains, but it's likely the issue would persist.
If you call down a rescue drone for an animal as Operator, you are able to use transference to then go into a necramech. When you exit the mech, you lose the ability to switch back to operator or to enter the mech again. Transference becomes usable again in the openworld's relay, but remains unusable in the Drift itself until you return to the orbiter. Transference (or at least into anything except a warframe) should not be usable while capturing animals. I haven't tested this outside solo or in the Vallis/Plains, but it's likely the issue would persist.