Hi there, welcome!
How long ago were they spayed/neutered? It can take a long time for female hormones to settle after spaying.
Also, did you do any pre-bonding (cage swapping, etc)?
How many sessions did you do for your step 3? It sounds like maybe only a couple sessions?
Assuming Robin was spayed long enough ago (I think 4-6 weeks is recommended), I would keep up with whatever was working, and it sounds like step 3 was working! You really want to cement positive behaviors in one situation before moving to a new location.
Was step 2 also in a neutral area?
Bonding is stressful, for both you and your bunnies, but it is worth it in the end. Just be sure to give each bunny some extra love outside of the sessions and make sure they are staying healthy (eating and pooping well).
My first pair took 3 months to bond fully, and stress bonding for the first few weeks was necessary as they would try to fight. We did car rides in a plastic tub (with an assistant of course), and progressed to the bath tub and bathroom. Progress tends to come in steps, rather than a gradual improvement. With my two, it seemed like they would hate each other forever. Then after a couple weeks of stress sessions (which made me feel like the worst person ever, believe me!) they decided they didnt want to fight any more…. we progressed to longer and longer sessions in my bathroom, with them ignoring each other. Took them to my office for a few very long, 6-8 hour sessions in a larger pen but a super neutral area. Then, a few days later in the bathroom, there was some grooming, and then after a few more days they were madly in love and groomed and cuddled constantly. And neither of them held any grudges against me! 
There can definitely be a lot of self doubt, but it sounds like you have had some positive sessions, so keep at it and be patient!
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.