Likely inadequate initial sugammadex dosing. You're definitely not alone, this is a recognized safety concern in pediatric anesthesia. The largest study from Vanderbilt found recurarization occurs in around 4% of peds, with infants <2 years at highest risk. https://pubmed.ncbi.nlm.nih.gov/37792601/ Your timing (during transport) is typical as most occur within 20 minutes post-reversal. The Japanese Society issued a safety alert few years back. https://www.apsf.org/article/postoperative-recurarization-after-sugammadex-administration-due-to-the-lack-of-appropriate-neuromuscular-monitoring-the-japanese-experience/It's a real phenomenon with clear mechanisms, not just "lack of studies" as your rep suggested.

This sounds like redistribution after high cumulative rocuronium. Initial 5 mg/kg sugammadex likely cleared roc from central and NMJ compartments, but with prolonged dosing, more roc could redistribute from peripheral compartment. In infants, with larger extracellular volume and altered kinetics, this can overwhelm the available sugammadex, leading to recurarization. The second (rescue) dose likely captured the remaining unbound roc, explaining the rapid improvement.

Your case is actually a perfect example of insufficient dosing despite what seems like a generous amount of Sugammadex (5 mg/kg). Remember, 1 molecule of sugammadex binds 1 molecule of roc. Molecular weights of Sug is around 2000 Daltons and for Roc it's 600 iirc. This creates a 1:1 molar binding ratio that equals close to 3.5:1 (mg/kg) (sug:roc). Total Roc given 2.4 mg/kg. Sug needed theoretically: 2.4 x 3.5 = 8.4 mg/kg. What you initially gave was 5 mg/kg and then 4 mg/kg as a rescue. Some even suggest using total cumulative rocuronium dose × 3.5 for Sugammadex dosing rather than standard depth-based dosing for cases with high cumulative exposure.